code: def build_model(self) -> BlenderBot2FidModel:
      if self.generation_model == "t5":
          model = T5BlenderBot2FidModel(self.opt, self.dict)
      else:
          model = BlenderBot2FidModel(self.opt, self.dict)
      if self.opt["embedding_type"] != "random":
          self._copy_embeddings(
              model.encoder.embeddings.weight,
              self.opt["embedding_type"],
          )
      return model
  
imports: import torch
  from torch.nn import CrossEntropyLoss
  from torch.distributions.categorical import Categorical
  from typing import Optional, Dict, Union, Tuple, Any
  from parlai.core.message import Message
  from parlai.core.opt import Opt
  from parlai.core.params import ParlaiParser
  from parlai.agents.transformer.transformer import TransformerGeneratorAgent
  from parlai.agents.fid.fid import FidAgent
  from parlai.core.torch_generator_agent import PPLMetric, TorchGeneratorAgent
  from parlai.core.metrics import AverageMetric
  from parlai.agents.fid.fid import WizIntGoldDocRetrieverFiDAgent
  from projects.blenderbot2.agents.blenderbot2 import BlenderBot2FidAgent, BlenderBot2FidModel, T5BlenderBot2FidModel
  from projects.seeker.agents.seeker import ComboFidAgent
label_desc: Use image node_id 2 for calling the ContrastiveBB2Agent obj's underlying member method code with example usage: obj.build_model() and returns: model