docstr: This method calls the parent class's batchify method and then add
  classifier_label and is_ltr property to the the batch.
docstr_tok: ["This","method","calls","the","parent","class","'s","batchify","method","and","then","add","classifier_label","and","is_ltr","property","to","the","the","batch","."]
code: def batchify(self, obs_batch, sort=False):
      """
      This method calls the parent class's batchify method and then add
      classifier_label and is_ltr property to the the batch.
      """
      batch = super().batchify(obs_batch, sort=sort)
  
      if batch.valid_indices is None:
          return batch
  
      batch.classifier_label = torch.tensor(
          [
              [obs_batch[i].get("classifier_label_idx", -1)]
              for i in batch.valid_indices
          ]
      )
      batch.is_ltr = torch.tensor(
          [
              [obs_batch[i].get("is_ltr", False)]
              for i in batch.valid_indices
          ]
      )
      return batch
  
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 5 for calling the ContrastiveTorchGeneratorAgent obj's underlying member method code with example usage: obj.batchify(obs_batch, sort) and returns: batch, batch