docs: def compile_pattern(word):
      """
      take a word pattern and return a Python regexp. A word pattern is a word
      with unknown letters replaced by a '?', e.g. 'di?ti??nar?'.
      """
      return re.compile(r'^%s$' % re.sub(r'\?', '[a-z]',
                                         dicts.sanitize_word(word)))