code: def contains_extractor(document):
      """A basic document feature extractor that returns a dict of words that
      the document contains.
      """
      tokens = _get_document_tokens(document)
      features = dict(("contains({0})".format(w), True) for w in tokens)
      return features
  
imports: from __future__ import absolute_import
  from itertools import chain
  import nltk
  from textblob.compat import basestring
  from textblob.decorators import cached_property
  from textblob.exceptions import FormatError
  from textblob.tokenizers import word_tokenize
  from textblob.utils import strip_punc, is_filelike
  import textblob.formats
label_desc: Use image node_id 4 for calling a global function with example usage: contains_extractor(document) and returns: features