class_docstr: Acts as the encoder for the FiD model.
  
  Custom Identity layer (as opposed to parlai.utils.torch.IdentityLayer) to account
  for special output required.
class_docstr_tok: ["Acts","as","the","encoder","for","the","FiD","model",".","Custom","Identity","layer","(","as","opposed","to","parlai.utils.torch.IdentityLayer",")","to","account","for","special","output","required","."]
code: def forward(self, input: torch.LongTensor, *args, **kwargs):
      return input, input.ne(self.pad_idx)
  
imports: from typing import Optional, Type, Tuple, List, Dict, Any
  import torch
  import torch.nn
  from parlai.agents.fid.fid import FidModel, concat_enc_outs
  from parlai.agents.hugging_face.gpt2 import GPT2Decoder, Gpt2Agent
  from parlai.agents.rag.args import RetrieverType
  from parlai.agents.rag.modules import RagModel
  from parlai.agents.rag.retrievers import Document, BLANK_DOC, SearchQuerySearchEngineRetriever, retriever_factory, RagRetriever
  from parlai.core.dict import DictionaryAgent
  from parlai.core.opt import Opt
  import parlai.utils.logging
  from projects.seeker.agents.seeker_modules import ComboFidSearchQuerySearchEngineRetriever
  from projects.seeker.agents.seeker_modules import combo_fid_retriever_factory, interleave_fid_combo_outputs, ComboFidModel
label_desc: Use image node_id 2 for calling the IdentityLayer obj's underlying member method code with example usage: obj.forward(input) and returns: input,  input