def video_extra_loss(self, frames_predicted, frames_target,
                       internal_states, video_features):
    """Optional video wide extra loss.

      If the model needs to calculate some extra loss across all predicted
      frames (e.g. in case of video GANS loss) override this function.

    Args:
      frames_predicted: list of all predicted frames.
      frames_target: list of all target frames.
      internal_states: internal states of the video.
      video_features: video wide features coming from video_features function.

    Returns:
      extra_loss: extra video side loss.
    """
    del frames_predicted, frames_target, internal_states, video_features
    return 0.0
Optional video wide extra loss.

      If the model needs to calculate some extra loss across all predicted
      frames (e.g. in case of video GANS loss) override this function.

    Args:
      frames_predicted: list of all predicted frames.
      frames_target: list of all target frames.
      internal_states: internal states of the video.
      video_features: video wide features coming from video_features function.

    Returns:
      extra_loss: extra video side loss.
    
tensor2tensor/models/video/base.py