code: def _path(opt):
      build(opt)
      dt = opt["datatype"].split(":")[0]
      if dt == "train":
          suffix = "train.14M+.txt"
      elif dt == "valid":
          suffix = "validation_NECN.20k.txt"
      else:
          suffix = "test_CN.10k.txt"
      return os.path.join(
          opt["datapath"], "BookTest", "booktest-gut", suffix
      )
  
file_path: ParlAI/parlai/tasks/booktest/agents.py
imports: from parlai.core.teachers import FbDeprecatedDialogTeacher
  from .build import build
  import copy
  import os
label_desc: Use image node_id 1 for calling a global function with example usage: _path(opt) and returns: os