code: def _file_name(prefix, lang):
      fname = prefix
      if lang is not None:
          fname += ".{lang}".format(lang=lang)
      return fname
  
imports: import logging
  import os
  import shutil
  import sys
  import typing
  from argparse import Namespace
  from itertools import zip_longest
  from fairseq import options, tasks, utils
  from fairseq.binarizer import AlignmentDatasetBinarizer, FileBinarizer, VocabularyDatasetBinarizer
  from fairseq.data import Dictionary
label_desc: Use image node_id 2 for calling a global function with example usage: _file_name(prefix, lang) and returns: fname