class_docstr: Second phase of decoder layer block
  This layer will take the input from the ecoder and phirst pass decoder.
  papers.nips.cc/paper/6775-deliberation-networks-sequence-generation-beyond-one-pass-decoding.pdf
code: def prepare_for_onnx_export_(self):
      self.onnx_trace = True
  
imports: import math
  import torch
  import torch.nn
  import torch.nn.functional
  from fairseq import options, utils
  from fairseq.models import FairseqEncoderDecoderModel, FairseqIncrementalDecoder, register_model, register_model_architecture
  from fairseq.models.transformer import Embedding, Linear, TransformerDecoder, TransformerEncoder
  from fairseq.modules import AdaptiveSoftmax, LayerNorm, MultiheadAttention, PositionalEmbedding, SinusoidalPositionalEmbedding
label_desc: Use image node_id 2 for calling the TransformerDecoderLayerPhase2 obj's underlying member method code with example usage: obj.prepare_for_onnx_export_() without return types