docstr: Run backwards decoder 
docstr_tok: ["Run","backwards","decoder"]
code: def _backward_pass(self, mel_specs, encoder_outputs, mask):
      """Run backwards decoder"""
      decoder_outputs_b, alignments_b, _ = self.decoder_backward(
          encoder_outputs,
          torch.flip(mel_specs, dims=(1,)),
          mask,
          self.speaker_embeddings_projected,
      )
      decoder_outputs_b = decoder_outputs_b.transpose(1, 2).contiguous()
      return decoder_outputs_b, alignments_b
  
imports: import copy
  from abc import ABC, abstractmethod
  import torch
  from torch import nn
  from TTS.tts.utils.generic_utils import sequence_mask
label_desc: Use image node_id 9 for calling the TacotronAbstract obj's underlying member method code with example usage: obj._backward_pass(mel_specs, encoder_outputs, mask) and returns: decoder_outputs_b,  alignments_b