class_docstr: The FiD Model is a simpler version of the RAG Model.
  
  We override the encoder and decoder methods to join encoder outputs, and decode
  normally, respectively.
docstr: Decode, RAG-Style.
  
  :param input:
      input for the decoder
  :param encoder_state:
      RAG encoder states
  :param incr_state:
      incremental decoder state
  
  :return (output, new_incr_state):
      return the output token distribution, as well as new incremental state.
docstr_tok: ["Decode",",","RAG-Style",".",":","param","input",":","input","for","the","decoder",":","param","encoder_state",":","RAG","encoder","states",":","param","incr_state",":","incremental","decoder","state",":","return","(","output",",","new_incr_state",")",":","return","the","output","token","distribution",",","as","well","as","new","incremental","state","."]
code: def decoder(
      self,
      input: torch.LongTensor,
      encoder_state: Tuple[Any, ...],
      incr_state: Optional[Dict[str, Any]] = None,
  ) -> Tuple[torch.Tensor, Optional[Dict[str, Any]]]:
      """
      Decode, RAG-Style.
  
      :param input:
          input for the decoder
      :param encoder_state:
          RAG encoder states
      :param incr_state:
          incremental decoder state
  
      :return (output, new_incr_state):
          return the output token distribution, as well as new incremental state.
      """
      enc_out, enc_mask, *_ = encoder_state
      dec_out, incr_state = self.seq2seq_decoder(
          input, (enc_out, enc_mask), incr_state
      )  # type: ignore
      dec_out = self.decoder_output(dec_out)
      return dec_out, incr_state
  
imports: from abc import abstractmethod
  from copy import deepcopy
  import torch
  import random
  from typing import Tuple, Union, Optional, List, Dict, Any
  from parlai.core.dict import DictionaryAgent
  from parlai.core.opt import Opt
  from parlai.core.message import Message
  from parlai.agents.transformer.transformer import TransformerGeneratorModel
  from parlai.agents.rag.args import RetrieverType
  from parlai.agents.rag.modules import RagModel, Document, T5RagModel
  from parlai.agents.rag.rag import RagAgent
  from parlai.agents.rag.model_types import RagToken, get_forced_decoder_inputs, fix_incremental_state
  from parlai.utils.typing import TShared
  import parlai.utils.logging
  from parlai.tasks.wizard_of_internet import constants
label_desc: Use image node_id 5 for calling the FidModel obj's underlying member method code with example usage: obj.decoder(input, encoder_state, incr_state) and returns: dec_out,  incr_state