class_docstr: Override TorchRankerAgent to include label in fixed cands set.
  
  Necessary for certain IR tasks where given candidate set does not contain example
  labels.
class_docstr_tok: ["Override","TorchRankerAgent","to","include","label","in","fixed","cands","set",".","Necessary","for","certain","IR","tasks","where","given","candidate","set","does","not","contain","example","labels","."]
docstr: Override to clean up candidates.
docstr_tok: ["Override","to","clean","up","candidates","."]
code: def eval_step(self, batch):
      """
      Override to clean up candidates.
      """
      output = super().eval_step(batch)
      if self.eval_candidates == "fixed":
          self.fixed_candidates = self.fixed_candidates[
              : self.num_fixed_candidates
          ]
      return output
  
imports: from typing import Optional
  from parlai.core.params import ParlaiParser
  from parlai.core.opt import Opt
  import torch
  from .transformer import TransformerRankerAgent
  from parlai.core.torch_ranker_agent import TorchRankerAgent
label_desc: Use image node_id 5 for calling the AddLabelFixedCandsTRA obj's underlying member method code with example usage: obj.eval_step(batch) and returns: output