code: def _path(opt, persona):
      # Build the data if it doesn't exist.
      build(opt)
      dt = opt["datatype"].split(":")[0] + "_" + persona
      return os.path.join(
          opt["datapath"], "Persona-Chat", "personachat", dt + ".txt"
      )
  
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, persona) and returns: os