code: def _get_file_or_model_specifiable_agent(self, prefix, opt):
      if len(opt.get(f"{prefix}_model_file", "")) > 0:
          if len(opt.get(f"{prefix}_model", "")) > 0:
              raise KeyError(
                  "Both `--{prefix}-model-file` and `--{prefix}-model` specified. Exactly one should be."
              )
          model = self._make_agent(
              opt,
              f"{prefix}_model_file",
              requireModelExists=True,
              opt_key="model_file",
          )
      elif len(opt.get(f"{prefix}_model", "")) > 0:
          model = self._make_agent(opt, f"{prefix}_model", "")
      else:
          raise KeyError(
              f"Both `--{prefix}-model-file` and `--{prefix}-model` specified. Neither currently set."
          )
      return model
  
imports: import json
  from copy import deepcopy
  from shutil import copyfile
  import os
  import parlai.utils.logging
  import parlai.core.tod.tod_world
  import parlai.core.tod.tod_agents
  from parlai.core.agents import create_agent
  from parlai.core.metrics import dict_report, aggregate_unnamed_reports
  from parlai.core.opt import Opt
  from parlai.core.params import ParlaiParser
  from parlai.core.script import ParlaiScript, register_script
  from parlai.utils.distributed import is_primary_worker, all_gather_list, is_distributed, get_rank, sync_object, num_workers
  from parlai.utils.io import PathManager
  from parlai.utils.misc import TimeLogger, nice_report
  from parlai.utils.world_logging import WorldLogger
label_desc: Use image node_id 3 for calling the TodWorldScript obj's underlying member method code with example usage: obj._get_file_or_model_specifiable_agent(prefix, opt) and returns: model