# coding=utf-8
# Copyright 2022 Meta and The HuggingFace Inc. team. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
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"""PyTorch TimeSformer model."""

import collections
from typing import Optional, Union

import torch
import torch.nn.functional
from torch import nn
from torch.nn import BCEWithLogitsLoss, CrossEntropyLoss, MSELoss

from ...activations import ACT2FN
from ...modeling_layers import GradientCheckpointingLayer
from ...modeling_outputs import BaseModelOutput, ImageClassifierOutput
from ...modeling_utils import PreTrainedModel
from ...utils import (
    auto_docstring,
    logging,
)
from .configuration_timesformer import TimesformerConfig


logger = logging.get_logger(__name__)


# Adapted from https://github.com/facebookresearch/TimeSformer/blob/a5ef29a7b7264baff199a30b3306ac27de901133/timesformer/models/vit.py#L155
class TimesformerPatchEmbeddings(nn.Module):
    """Image to Patch Embedding"""

    def __init__(self, config):
        super().__init__()

        image_size = config.image_size
        patch_size = config.patch_size

        image_size = image_size if isinstance(image_size, collections.abc.Iterable) else (image_size, image_size)
        patch_size = patch_size if isinstance(patch_size, collections.abc.Iterable) else (patch_size, patch_size)

        num_patches = (image_size[1] // patch_size[1]) * (image_size[0] // patch_size[0])
        self.image_size = image_size
        self.patch_size = patch_size
        self.num_patches = num_patches

        self.projection = nn.Conv2d(config.num_channels, config.hidden_size, kernel_size=patch_size, stride=patch_size)

    def forward(self, pixel_values):
        batch_size, num_frames, num_channels, height, width = pixel_values.shape
        pixel_values = pixel_values.reshape(batch_size * num_frames, num_channels, height, width)

        embeddings = self.projection(pixel_values)
        patch_width = embeddings.size(-1)
        embeddings = embeddings.flatten(2).transpose(1, 2)
        return embeddings, num_frames, patch_width


class TimesformerEmbeddings(nn.Module):
    """
    Construct the patch and position embeddings.
    """

    def __init__(self, config):
        super().__init__()

        embed_dim = config.hidden_size
        num_frames = config.num_frames
        drop_rate = config.hidden_dropout_prob
        attention_type = config.attention_type

        self.attention_type = attention_type
        self.patch_embeddings = TimesformerPatchEmbeddings(config)
        self.num_patches = self.patch_embeddings.num_patches

        # Positional Embeddings
        self.cls_token = nn.Parameter(torch.zeros(1, 1, embed_dim))
        self.position_embeddings = nn.Parameter(torch.zeros(1, self.num_patches + 1, embed_dim))
        self.pos_drop = nn.Dropout(p=drop_rate)
        if attention_type != "space_only":
            self.time_embeddings = nn.Parameter(torch.zeros(1, num_frames, embed_dim))
            self.time_drop = nn.Dropout(p=drop_rate)

    def forward(self, pixel_values):
        batch_size = pixel_values.shape[0]

        # create patch embeddings
        embeddings, num_frames, patch_width = self.patch_embeddings(pixel_values)

        cls_tokens = self.cls_token.expand(embeddings.size(0), -1, -1)
        embeddings = torch.cat((cls_tokens, embeddings), dim=1)

        # resizing the positional embeddings in case they don't match the input at inference
        if embeddings.size(1) != self.position_embeddings.size(1):
            position_embeddings = self.position_embeddings
            cls_pos_embed = position_embeddings[0, 0, :].unsqueeze(0).unsqueeze(1)
            other_pos_embed = position_embeddings[0, 1:, :].unsqueeze(0).transpose(1, 2)
            patch_num = int(other_pos_embed.size(2) ** 0.5)
            patch_height = embeddings.size(1) // patch_width
            other_pos_embed = other_pos_embed.reshape(1, embeddings.size(2), patch_num, patch_num)
            new_pos_embed = nn.functional.interpolate(
                other_pos_embed, size=(patch_height, patch_width), mode="nearest"
            )
            new_pos_embed = new_pos_embed.flatten(2)
            new_pos_embed = new_pos_embed.transpose(1, 2)
            new_pos_embed = torch.cat((cls_pos_embed, new_pos_embed), 1)
            embeddings = embeddings + new_pos_embed
        else:
            embeddings = embeddings + self.position_embeddings
        embeddings = self.pos_drop(embeddings)

        # Time Embeddings
        if self.attention_type != "space_only":
            cls_tokens = embeddings[:batch_size, 0, :].unsqueeze(1)
            embeddings = embeddings[:, 1:]
            _, patch_height, patch_width = embeddings.shape
            embeddings = (
                embeddings.reshape(batch_size, num_frames, patch_height, patch_width)
                .permute(0, 2, 1, 3)
                .reshape(batch_size * patch_height, num_frames, patch_width)
            )
            # Resizing time embeddings in case they don't match
            if num_frames != self.time_embeddings.size(1):
                time_embeddings = self.time_embeddings.transpose(1, 2)
                new_time_embeddings = nn.functional.interpolate(time_embeddings, size=(num_frames), mode="nearest")
                new_time_embeddings = new_time_embeddings.transpose(1, 2)
                embeddings = embeddings + new_time_embeddings
            else:
                embeddings = embeddings + self.time_embeddings
            embeddings = self.time_drop(embeddings)
            embeddings = embeddings.view(batch_size, patch_height, num_frames, patch_width).reshape(
                batch_size, patch_height * num_frames, patch_width
            )
            embeddings = torch.cat((cls_tokens, embeddings), dim=1)

        return embeddings


# Copied from transformers.models.beit.modeling_beit.drop_path
def drop_path(input: torch.Tensor, drop_prob: float = 0.0, training: bool = False) -> torch.Tensor:
    """
    Drop paths (Stochastic Depth) per sample (when applied in main path of residual blocks).

    Comment by Ross Wightman: This is the same as the DropConnect impl I created for EfficientNet, etc networks,
    however, the original name is misleading as 'Drop Connect' is a different form of dropout in a separate paper...
    See discussion: https://github.com/tensorflow/tpu/issues/494#issuecomment-532968956 ... I've opted for changing the
    layer and argument names to 'drop path' rather than mix DropConnect as a layer name and use 'survival rate' as the
    argument.
    """
    if drop_prob == 0.0 or not training:
        return input
    keep_prob = 1 - drop_prob
    shape = (input.shape[0],) + (1,) * (input.ndim - 1)  # work with diff dim tensors, not just 2D ConvNets
    random_tensor = keep_prob + torch.rand(shape, dtype=input.dtype, device=input.device)
    random_tensor.floor_()  # binarize
    output = input.div(keep_prob) * random_tensor
    return output


# Copied from transformers.models.beit.modeling_beit.BeitDropPath with Beit->TimeSformer
class TimeSformerDropPath(nn.Module):
    """Drop paths (Stochastic Depth) per sample (when applied in main path of residual blocks)."""

    def __init__(self, drop_prob: Optional[float] = None) -> None:
        super().__init__()
        self.drop_prob = drop_prob

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        return drop_path(hidden_states, self.drop_prob, self.training)

    def extra_repr(self) -> str:
        return f"p={self.drop_prob}"


# Adapted from https://github.com/facebookresearch/TimeSformer/blob/a5ef29a7b7264baff199a30b3306ac27de901133/timesformer/models/vit.py#L57
class TimesformerSelfAttention(nn.Module):
    def __init__(self, config: TimesformerConfig):
        super().__init__()

        num_heads = config.num_attention_heads
        qkv_bias = config.qkv_bias
        attention_dropout_prob = config.attention_probs_dropout_prob

        self.num_heads = num_heads
        head_dim = config.hidden_size // num_heads
        self.scale = head_dim**-0.5
        self.qkv = nn.Linear(config.hidden_size, config.hidden_size * 3, bias=qkv_bias)
        self.attn_drop = nn.Dropout(attention_dropout_prob)

    def forward(self, hidden_states, output_attentions: bool = False):
        batch_size, hidden_size, num_channels = hidden_states.shape
        qkv = (
            self.qkv(hidden_states)
            .reshape(batch_size, hidden_size, 3, self.num_heads, num_channels // self.num_heads)
            .permute(2, 0, 3, 1, 4)
        )
        query, key, value = qkv[0], qkv[1], qkv[2]

        attention_probs = (query @ key.transpose(-2, -1)) * self.scale
        attention_probs = attention_probs.softmax(dim=-1)
        attention_probs = self.attn_drop(attention_probs)

        context_layer = (attention_probs @ value).transpose(1, 2).reshape(batch_size, hidden_size, num_channels)

        outputs = (context_layer, attention_probs) if output_attentions else (context_layer,)

        return outputs


class TimesformerSelfOutput(nn.Module):
    """
    The residual connection is defined in TimesformerLayer instead of here (as is the case with other models), due to
    the layernorm applied before each block.
    """

    def __init__(self, config: TimesformerConfig) -> None:
        super().__init__()
        self.dense = nn.Linear(config.hidden_size, config.hidden_size)
        self.dropout = nn.Dropout(config.hidden_dropout_prob)

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        hidden_states = self.dense(hidden_states)
        hidden_states = self.dropout(hidden_states)

        return hidden_states


class TimeSformerAttention(nn.Module):
    def __init__(self, config: TimesformerConfig) -> None:
        super().__init__()
        self.attention = TimesformerSelfAttention(config)
        self.output = TimesformerSelfOutput(config)

    def forward(
        self,
        hidden_states: torch.Tensor,
        output_attentions: bool = False,
    ) -> Union[tuple[torch.Tensor, torch.Tensor], tuple[torch.Tensor]]:
        self_outputs = self.attention(hidden_states, output_attentions)

        attention_output = self.output(self_outputs[0])

        outputs = (attention_output,) + self_outputs[1:]  # add attentions if we output them
        return outputs


# Adapted from https://github.com/facebookresearch/TimeSformer/blob/a5ef29a7b7264baff199a30b3306ac27de901133/timesformer/models/vit.py#L39
class TimesformerIntermediate(nn.Module):
    def __init__(self, config: TimesformerConfig) -> None:
        super().__init__()
        self.dense = nn.Linear(config.hidden_size, config.intermediate_size)
        self.dropout = nn.Dropout(config.hidden_dropout_prob)

        if isinstance(config.hidden_act, str):
            self.intermediate_act_fn = ACT2FN[config.hidden_act]
        else:
            self.intermediate_act_fn = config.hidden_act

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        hidden_states = self.dense(hidden_states)
        hidden_states = self.intermediate_act_fn(hidden_states)
        hidden_states = self.dropout(hidden_states)

        return hidden_states


class TimesformerOutput(nn.Module):
    def __init__(self, config: TimesformerConfig) -> None:
        super().__init__()
        self.dense = nn.Linear(config.intermediate_size, config.hidden_size)
        self.dropout = nn.Dropout(config.hidden_dropout_prob)

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        hidden_states = self.dense(hidden_states)
        hidden_states = self.dropout(hidden_states)

        return hidden_states


# Adapted from https://github.com/facebookresearch/TimeSformer/blob/a5ef29a7b7264baff199a30b3306ac27de901133/timesformer/models/vit.py#L89
class TimesformerLayer(GradientCheckpointingLayer):
    def __init__(self, config: TimesformerConfig, layer_index: int) -> None:
        super().__init__()

        attention_type = config.attention_type

        drop_path_rates = [
            x.item() for x in torch.linspace(0, config.drop_path_rate, config.num_hidden_layers, device="cpu")
        ]  # stochastic depth decay rule
        drop_path_rate = drop_path_rates[layer_index]

        self.drop_path = TimeSformerDropPath(drop_path_rate) if drop_path_rate > 0.0 else nn.Identity()
        self.attention = TimeSformerAttention(config)
        self.intermediate = TimesformerIntermediate(config)
        self.output = TimesformerOutput(config)
        self.layernorm_before = nn.LayerNorm(config.hidden_size, eps=config.layer_norm_eps)
        self.layernorm_after = nn.LayerNorm(config.hidden_size, eps=config.layer_norm_eps)

        self.config = config
        self.attention_type = attention_type
        if attention_type not in ["divided_space_time", "space_only", "joint_space_time"]:
            raise ValueError(f"Unknown attention type: {attention_type}")

        # Temporal Attention Parameters
        if self.attention_type == "divided_space_time":
            self.temporal_layernorm = nn.LayerNorm(config.hidden_size, eps=config.layer_norm_eps)
            self.temporal_attention = TimeSformerAttention(config)
            self.temporal_dense = nn.Linear(config.hidden_size, config.hidden_size)

    def forward(self, hidden_states: torch.Tensor, output_attentions: bool = False):
        num_frames = self.config.num_frames
        num_patch_width = self.config.image_size // self.config.patch_size
        batch_size = hidden_states.shape[0]
        num_spatial_tokens = (hidden_states.size(1) - 1) // num_frames
        num_patch_height = num_spatial_tokens // num_patch_width

        if self.attention_type in ["space_only", "joint_space_time"]:
            self_attention_outputs = self.attention(
                self.layernorm_before(hidden_states), output_attentions=output_attentions
            )
            attention_output = self_attention_outputs[0]
            outputs = self_attention_outputs[1:]  # add self attentions if we output attention weights

            hidden_states = hidden_states + self.drop_path(attention_output)

            layer_output = self.layernorm_after(hidden_states)
            layer_output = self.intermediate(layer_output)
            layer_output = self.output(layer_output)
            layer_output = hidden_states + self.drop_path(layer_output)

            outputs = (layer_output,) + outputs

            return outputs

        elif self.attention_type == "divided_space_time":
            # Temporal
            temporal_embedding = hidden_states[:, 1:, :]
            temporal_embedding = temporal_embedding.reshape(
                batch_size, num_patch_height, num_patch_width, num_frames, temporal_embedding.shape[2]
            ).reshape(batch_size * num_patch_height * num_patch_width, num_frames, temporal_embedding.shape[2])

            temporal_attention_outputs = self.temporal_attention(
                self.temporal_layernorm(temporal_embedding),
            )
            attention_output = temporal_attention_outputs[0]

            residual_temporal = self.drop_path(attention_output)

            residual_temporal = residual_temporal.reshape(
                batch_size, num_patch_height, num_patch_width, num_frames, residual_temporal.shape[2]
            ).reshape(batch_size, num_patch_height * num_patch_width * num_frames, residual_temporal.shape[2])
            residual_temporal = self.temporal_dense(residual_temporal)
            temporal_embedding = hidden_states[:, 1:, :] + residual_temporal

            # Spatial
            init_cls_token = hidden_states[:, 0, :].unsqueeze(1)
            cls_token = init_cls_token.repeat(1, num_frames, 1)
            cls_token = cls_token.reshape(batch_size * num_frames, 1, cls_token.shape[2])
            spatial_embedding = temporal_embedding
            spatial_embedding = (
                spatial_embedding.reshape(
                    batch_size, num_patch_height, num_patch_width, num_frames, spatial_embedding.shape[2]
                )
                .permute(0, 3, 1, 2, 4)
                .reshape(batch_size * num_frames, num_patch_height * num_patch_width, spatial_embedding.shape[2])
            )
            spatial_embedding = torch.cat((cls_token, spatial_embedding), 1)

            spatial_attention_outputs = self.attention(
                self.layernorm_before(spatial_embedding), output_attentions=output_attentions
            )
            attention_output = spatial_attention_outputs[0]
            outputs = spatial_attention_outputs[1:]  # add self attentions if we output attention weights

            residual_spatial = self.drop_path(attention_output)

            # Taking care of CLS token
            cls_token = residual_spatial[:, 0, :]
            cls_token = cls_token.reshape(batch_size, num_frames, cls_token.shape[1])
            cls_token = torch.mean(cls_token, 1, True)  # averaging for every frame
            residual_spatial = residual_spatial[:, 1:, :]
            residual_spatial = (
                residual_spatial.reshape(
                    batch_size, num_frames, num_patch_height, num_patch_width, residual_spatial.shape[2]
                )
                .permute(0, 2, 3, 1, 4)
                .reshape(batch_size, num_patch_height * num_patch_width * num_frames, residual_spatial.shape[2])
            )
            residual = residual_spatial
            hidden_states = temporal_embedding

            # Mlp
            hidden_states = torch.cat((init_cls_token, hidden_states), 1) + torch.cat((cls_token, residual), 1)
            layer_output = self.layernorm_after(hidden_states)
            layer_output = self.intermediate(layer_output)
            layer_output = self.output(layer_output)
            layer_output = hidden_states + self.drop_path(layer_output)

            outputs = (layer_output,) + outputs

            return outputs


class TimesformerEncoder(nn.Module):
    def __init__(self, config: TimesformerConfig) -> None:
        super().__init__()
        self.config = config
        self.layer = nn.ModuleList([TimesformerLayer(config, ind) for ind in range(config.num_hidden_layers)])
        self.gradient_checkpointing = False

    def forward(
        self,
        hidden_states: torch.Tensor,
        output_attentions: bool = False,
        output_hidden_states: bool = False,
        return_dict: bool = True,
    ) -> Union[tuple, BaseModelOutput]:
        all_hidden_states = () if output_hidden_states else None
        all_self_attentions = () if output_attentions else None

        for i, layer_module in enumerate(self.layer):
            if output_hidden_states:
                all_hidden_states = all_hidden_states + (hidden_states,)

            layer_outputs = layer_module(hidden_states, output_attentions)

            hidden_states = layer_outputs[0]

            if output_attentions:
                all_self_attentions = all_self_attentions + (layer_outputs[1],)

        if output_hidden_states:
            all_hidden_states = all_hidden_states + (hidden_states,)

        if not return_dict:
            return tuple(v for v in [hidden_states, all_hidden_states, all_self_attentions] if v is not None)
        return BaseModelOutput(
            last_hidden_state=hidden_states,
            hidden_states=all_hidden_states,
            attentions=all_self_attentions,
        )


@auto_docstring
class TimesformerPreTrainedModel(PreTrainedModel):
    config: TimesformerConfig
    base_model_prefix = "timesformer"
    main_input_name = "pixel_values"
    supports_gradient_checkpointing = True
    _no_split_modules = ["TimesformerLayer"]

    def _init_weights(self, module):
        if isinstance(module, (nn.Linear, nn.Conv2d)):
            nn.init.trunc_normal_(module.weight, std=self.config.initializer_range)
            if module.bias is not None:
                nn.init.constant_(module.bias, 0)
        elif isinstance(module, nn.LayerNorm):
            nn.init.constant_(module.bias, 0)
            nn.init.constant_(module.weight, 1.0)
        elif isinstance(module, TimesformerEmbeddings):
            nn.init.trunc_normal_(module.cls_token, std=self.config.initializer_range)
            nn.init.trunc_normal_(module.position_embeddings, std=self.config.initializer_range)
            module.patch_embeddings.apply(self._init_weights)


@auto_docstring
class TimesformerModel(TimesformerPreTrainedModel):
    def __init__(self, config):
        super().__init__(config)
        self.config = config

        self.embeddings = TimesformerEmbeddings(config)
        self.encoder = TimesformerEncoder(config)

        self.layernorm = nn.LayerNorm(config.hidden_size, eps=config.layer_norm_eps)

        # Initialize weights and apply final processing
        self.post_init()

    def get_input_embeddings(self):
        return self.embeddings.patch_embeddings

    def _prune_heads(self, heads_to_prune):
        """
        Prunes heads of the model. heads_to_prune: dict of {layer_num: list of heads to prune in this layer} See base
        class PreTrainedModel
        """
        for layer, heads in heads_to_prune.items():
            self.encoder.layer[layer].attention.prune_heads(heads)

    @auto_docstring
    def forward(
        self,
        pixel_values: torch.FloatTensor,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[tuple[torch.FloatTensor], BaseModelOutput]:
        r"""
        Examples:

        ```python
        >>> import av
        >>> import numpy as np

        >>> from transformers import AutoImageProcessor, TimesformerModel
        >>> from huggingface_hub import hf_hub_download

        >>> np.random.seed(0)


        >>> def read_video_pyav(container, indices):
        ...     '''
        ...     Decode the video with PyAV decoder.
        ...     Args:
        ...         container (`av.container.input.InputContainer`): PyAV container.
        ...         indices (`list[int]`): List of frame indices to decode.
        ...     Returns:
        ...         result (np.ndarray): np array of decoded frames of shape (num_frames, height, width, 3).
        ...     '''
        ...     frames = []
        ...     container.seek(0)
        ...     start_index = indices[0]
        ...     end_index = indices[-1]
        ...     for i, frame in enumerate(container.decode(video=0)):
        ...         if i > end_index:
        ...             break
        ...         if i >= start_index and i in indices:
        ...             frames.append(frame)
        ...     return np.stack([x.to_ndarray(format="rgb24") for x in frames])


        >>> def sample_frame_indices(clip_len, frame_sample_rate, seg_len):
        ...     '''
        ...     Sample a given number of frame indices from the video.
        ...     Args:
        ...         clip_len (`int`): Total number of frames to sample.
        ...         frame_sample_rate (`int`): Sample every n-th frame.
        ...         seg_len (`int`): Maximum allowed index of sample's last frame.
        ...     Returns:
        ...         indices (`list[int]`): List of sampled frame indices
        ...     '''
        ...     converted_len = int(clip_len * frame_sample_rate)
        ...     end_idx = np.random.randint(converted_len, seg_len)
        ...     start_idx = end_idx - converted_len
        ...     indices = np.linspace(start_idx, end_idx, num=clip_len)
        ...     indices = np.clip(indices, start_idx, end_idx - 1).astype(np.int64)
        ...     return indices


        >>> # video clip consists of 300 frames (10 seconds at 30 FPS)
        >>> file_path = hf_hub_download(
        ...     repo_id="nielsr/video-demo", filename="eating_spaghetti.mp4", repo_type="dataset"
        ... )
        >>> container = av.open(file_path)

        >>> # sample 8 frames
        >>> indices = sample_frame_indices(clip_len=8, frame_sample_rate=4, seg_len=container.streams.video[0].frames)
        >>> video = read_video_pyav(container, indices)

        >>> image_processor = AutoImageProcessor.from_pretrained("MCG-NJU/videomae-base")
        >>> model = TimesformerModel.from_pretrained("facebook/timesformer-base-finetuned-k400")

        >>> # prepare video for the model
        >>> inputs = image_processor(list(video), return_tensors="pt")

        >>> # forward pass
        >>> outputs = model(**inputs)
        >>> last_hidden_states = outputs.last_hidden_state
        >>> list(last_hidden_states.shape)
        [1, 1569, 768]
        ```"""
        output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        embedding_output = self.embeddings(pixel_values)

        encoder_outputs = self.encoder(
            embedding_output,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )
        sequence_output = encoder_outputs[0]
        if self.layernorm is not None:
            sequence_output = self.layernorm(sequence_output)

        if not return_dict:
            return (sequence_output,) + encoder_outputs[1:]

        return BaseModelOutput(
            last_hidden_state=sequence_output,
            hidden_states=encoder_outputs.hidden_states,
            attentions=encoder_outputs.attentions,
        )


@auto_docstring(
    custom_intro="""
        TimeSformer Model transformer with a video classification head on top (a linear layer on top of the final hidden state
    of the [CLS] token) e.g. for ImageNet.
    """
)
class TimesformerForVideoClassification(TimesformerPreTrainedModel):
    def __init__(self, config):
        super().__init__(config)

        self.num_labels = config.num_labels
        self.timesformer = TimesformerModel(config)

        # Classifier head
        self.classifier = nn.Linear(config.hidden_size, config.num_labels) if config.num_labels > 0 else nn.Identity()

        # Initialize weights and apply final processing
        self.post_init()

    @auto_docstring
    def forward(
        self,
        pixel_values: Optional[torch.Tensor] = None,
        labels: Optional[torch.Tensor] = None,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[tuple, ImageClassifierOutput]:
        r"""
        labels (`torch.LongTensor` of shape `(batch_size,)`, *optional*):
            Labels for computing the image classification/regression loss. Indices should be in `[0, ...,
            config.num_labels - 1]`. If `config.num_labels == 1` a regression loss is computed (Mean-Square loss), If
            `config.num_labels > 1` a classification loss is computed (Cross-Entropy).

        Examples:

        ```python
        >>> import av
        >>> import torch
        >>> import numpy as np

        >>> from transformers import AutoImageProcessor, TimesformerForVideoClassification
        >>> from huggingface_hub import hf_hub_download

        >>> np.random.seed(0)


        >>> def read_video_pyav(container, indices):
        ...     '''
        ...     Decode the video with PyAV decoder.
        ...     Args:
        ...         container (`av.container.input.InputContainer`): PyAV container.
        ...         indices (`list[int]`): List of frame indices to decode.
        ...     Returns:
        ...         result (np.ndarray): np array of decoded frames of shape (num_frames, height, width, 3).
        ...     '''
        ...     frames = []
        ...     container.seek(0)
        ...     start_index = indices[0]
        ...     end_index = indices[-1]
        ...     for i, frame in enumerate(container.decode(video=0)):
        ...         if i > end_index:
        ...             break
        ...         if i >= start_index and i in indices:
        ...             frames.append(frame)
        ...     return np.stack([x.to_ndarray(format="rgb24") for x in frames])


        >>> def sample_frame_indices(clip_len, frame_sample_rate, seg_len):
        ...     '''
        ...     Sample a given number of frame indices from the video.
        ...     Args:
        ...         clip_len (`int`): Total number of frames to sample.
        ...         frame_sample_rate (`int`): Sample every n-th frame.
        ...         seg_len (`int`): Maximum allowed index of sample's last frame.
        ...     Returns:
        ...         indices (`list[int]`): List of sampled frame indices
        ...     '''
        ...     converted_len = int(clip_len * frame_sample_rate)
        ...     end_idx = np.random.randint(converted_len, seg_len)
        ...     start_idx = end_idx - converted_len
        ...     indices = np.linspace(start_idx, end_idx, num=clip_len)
        ...     indices = np.clip(indices, start_idx, end_idx - 1).astype(np.int64)
        ...     return indices


        >>> # video clip consists of 300 frames (10 seconds at 30 FPS)
        >>> file_path = hf_hub_download(
        ...     repo_id="nielsr/video-demo", filename="eating_spaghetti.mp4", repo_type="dataset"
        ... )
        >>> container = av.open(file_path)

        >>> # sample 8 frames
        >>> indices = sample_frame_indices(clip_len=8, frame_sample_rate=1, seg_len=container.streams.video[0].frames)
        >>> video = read_video_pyav(container, indices)

        >>> image_processor = AutoImageProcessor.from_pretrained("MCG-NJU/videomae-base-finetuned-kinetics")
        >>> model = TimesformerForVideoClassification.from_pretrained("facebook/timesformer-base-finetuned-k400")

        >>> inputs = image_processor(list(video), return_tensors="pt")

        >>> with torch.no_grad():
        ...     outputs = model(**inputs)
        ...     logits = outputs.logits

        >>> # model predicts one of the 400 Kinetics-400 classes
        >>> predicted_label = logits.argmax(-1).item()
        >>> print(model.config.id2label[predicted_label])
        eating spaghetti
        ```"""
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        outputs = self.timesformer(
            pixel_values,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )

        sequence_output = outputs[0][:, 0]

        logits = self.classifier(sequence_output)

        loss = None
        if labels is not None:
            if self.config.problem_type is None:
                if self.num_labels == 1:
                    self.config.problem_type = "regression"
                elif self.num_labels > 1 and (labels.dtype == torch.long or labels.dtype == torch.int):
                    self.config.problem_type = "single_label_classification"
                else:
                    self.config.problem_type = "multi_label_classification"

            if self.config.problem_type == "regression":
                loss_fct = MSELoss()
                if self.num_labels == 1:
                    loss = loss_fct(logits.squeeze(), labels.squeeze())
                else:
                    loss = loss_fct(logits, labels)
            elif self.config.problem_type == "single_label_classification":
                loss_fct = CrossEntropyLoss()
                loss = loss_fct(logits.view(-1, self.num_labels), labels.view(-1))
            elif self.config.problem_type == "multi_label_classification":
                loss_fct = BCEWithLogitsLoss()
                loss = loss_fct(logits, labels)

        if not return_dict:
            output = (logits,) + outputs[1:]
            return ((loss,) + output) if loss is not None else output

        return ImageClassifierOutput(
            loss=loss,
            logits=logits,
            hidden_states=outputs.hidden_states,
            attentions=outputs.attentions,
        )


__all__ = ["TimesformerModel", "TimesformerForVideoClassification", "TimesformerPreTrainedModel"]