code: def _file_to_word_ids(filename, word_to_id):
      data = _read_words(filename)
      return [word_to_id[word] for word in data if word in word_to_id]
  
file_path: tensorpack/examples/PennTreebank/reader.py
imports: from __future__ import absolute_import, division, print_function
  import collections
  import os
  import tensorflow
label_desc: Use image node_id 3 for calling a global function with example usage: _file_to_word_ids(filename, word_to_id) and returns: unknown