code: def _path(task, opt):
      # Build the data if it doesn't exist.
      build(opt)
      suffix = ""
      dt = opt["datatype"].split(":")[0]
      if dt == "train":
          suffix = "train"
      elif dt == "test":
          suffix = "test_2500ex"
      elif dt == "valid":
          suffix = "valid_2000ex"
  
      return os.path.join(
          opt["datapath"],
          "CBT",
          "CBTest",
          "data",
          task + "_" + suffix + ".txt",
      )
  
imports: from parlai.core.teachers import FbDeprecatedDialogTeacher, MultiTaskTeacher
  from .build import build
  import copy
  import os
label_desc: Use image node_id 1 for calling a global function with example usage: _path(task, opt) and returns: os