class_docstr: Combo GPT2 Agent.
  
  This agent can handle retrieval for some contexts, and vanilla decoder-only
  computation for others.
class_docstr_tok: ["Combo","GPT2","Agent",".","This","agent","can","handle","retrieval","for","some","contexts",",","and","vanilla","decoder-only","computation","for","others","."]
docstr: Add Combo Args.
code: def add_cmdline_args(
      cls, parser: ParlaiParser, partial_opt: Optional[Opt] = None
  ) -> ParlaiParser:
      """
      Add Combo Args.
      """
      super().add_cmdline_args(parser, partial_opt)
      gpt2_combo = parser.add_argument_group("GPT2 Combo Group")
      gpt2_combo.add_argument(
          "--skip-retrieval-key",
          type=str,
          default="skip_retrieval",
          help="key in observation determining whether to skip retrieval.",
      )
  
imports: from typing import Optional, Tuple, List, Union
  import torch
  import torch.nn
  from parlai.agents.fid.fid import FidModel, FidAgent, SearchQuerySearchEngineFiDAgent, WizIntGoldDocRetrieverFiDAgent
  from parlai.agents.hugging_face.gpt2 import Gpt2Agent
  from parlai.agents.rag.rag import BaseGenerationAgentMixin
  from parlai.agents.rag.retrievers import Document
  from parlai.core.dict import DictionaryAgent
  from parlai.core.message import Message
  from parlai.core.opt import Opt
  from parlai.core.params import ParlaiParser
  from parlai.core.torch_agent import Batch, Output
  from parlai.core.torch_generator_agent import TorchGeneratorAgent
  from parlai.utils.torch import padded_tensor
  from projects.seeker.agents.seeker import SeekerAgent
  from projects.seeker.agents.gpt2_seeker_modules import GPT2WithRetrieverModel, ComboGPT2Model
label_desc: Use image node_id 1 for calling the GPT2ComboAgent obj's underlying member method code with example usage: obj.add_cmdline_args(cls, parser, partial_opt) without return types