    def output_layer(self, features, **kwargs):
        """
        Project features to the default output size, e.g., vocabulary size.

        Args:
            features (Tensor): features returned by *extract_features*.
        """
        raise NotImplementedError
Project features to the default output size, e.g., vocabulary size.

Args:
features (Tensor): features returned by *extract_features*.
fairseq/models/fairseq_decoder.py