code: def buffered_future_mask(self, tensor):
      dim = tensor.size(0)
      # self._future_mask.device != tensor.device is not working in TorchScript. This is a workaround.
      if (
          self._future_mask.size(0) == 0
          or (not self._future_mask.device == tensor.device)
          or self._future_mask.size(0) < dim
      ):
          self._future_mask = torch.triu(
              utils.fill_with_neg_inf(torch.zeros([dim, dim])), 1
          )
      self._future_mask = self._future_mask.to(tensor)
      return self._future_mask[:dim, :dim]
  
imports: import logging
  from typing import List, Optional
  import torch
  from torch import nn
  from fairseq import utils
  from fairseq.data.data_utils import lengths_to_padding_mask
  from fairseq.models import FairseqEncoder, FairseqEncoderDecoderModel, FairseqIncrementalDecoder, register_model, register_model_architecture
  from fairseq.models.text_to_speech.hub_interface import TTSHubInterface
  from fairseq.models.text_to_speech.tacotron2 import Postnet, Prenet
  from fairseq.modules import FairseqDropout, LayerNorm, PositionalEmbedding, TransformerDecoderLayer, TransformerEncoderLayer
label_desc: Use image node_id 5 for calling the TTSTransformerDecoder obj's underlying member method code with example usage: obj.buffered_future_mask(tensor) and returns: self