code: def __init__(self, opt, shared=None):
      self.opt = opt
      self.add_token_knowledge = opt["add_token_knowledge"]
      self.model_path = os.path.join(
          opt["datapath"],
          "models",
          "wizard_of_wikipedia",
          "full_dialogue_retrieval_model",
      )
  
      if not shared:
          # Create retriever
          download(
              opt["datapath"]
          )  # make sure to download all relevant files
          self._set_up_tfidf_retriever(opt)
          self._set_up_selector(opt)
      else:
          self.selector = create_agent_from_shared(shared["selector"])
          self.retriever = shared["retriever"]
          self.sent_tok = shared["sent_tok"]
          self.wiki_map = shared["wiki_map"]
  
      self.id = "KnowledgeRetrieverAgent"
  
      # NOTE: dialogue history should NOT be shared between instances
      self.retriever_history = {"episode_done": False}
      self.dialogue_history = []
      self.checked_sentence_history = []
  
imports: from typing import Optional
  from parlai.core.params import ParlaiParser
  from parlai.core.opt import Opt
  from parlai.core.agents import Agent, create_agent, create_agent_from_shared
  from parlai.core.torch_ranker_agent import TorchRankerAgent
  from parlai.tasks.wizard_of_wikipedia.agents import TOKEN_KNOWLEDGE
  from parlai.zoo.wizard_of_wikipedia.knowledge_retriever import download
  import json
  import os
label_desc: Use image node_id 2 to create a new KnowledgeRetrieverAgent object from inherited base classes: Agent with example: obj = KnowledgeRetrieverAgent(opt, shared)