code: def get_ptb_words_vocabulary():
      """Gets the Penn Tree Bank word vocabulary.
  
      Returns:
          dict: Dictionary that maps words to corresponding word IDs. The IDs are
          used in the Penn Tree Bank long sequence datasets.
  
      .. seealso::
         See :func:`get_ptb_words` for the actual datasets.
  
      """
      return _retrieve_word_vocabulary()
  
file_path: chainer/chainer/datasets/ptb.py
imports: import os
  import numpy
  from chainer.dataset import download
label_desc: Use image node_id 2 for calling a global function with example usage: get_ptb_words_vocabulary() and returns: _retrieve_word_vocabulary