class_docstr: Ad-hoc hack to recognize all punctuation and symbols.
class_docstr_tok: ["Ad-hoc","hack","to","recognize","all","punctuation","and","symbols","."]
code: def property_chars(self, prefix):
      # pylint:disable=no-self-use
      return "".join(
          six.unichr(x)
          for x in range(sys.maxunicode)
          if unicodedata.category(six.unichr(x)).startswith(prefix)
      )
  
file_path: texar/examples/transformer/bleu_tool.py
imports: from argparse import ArgumentParser
  from io import open
  import collections
  import math
  import re
  import sys
  import unicodedata
  import numpy
  import six
  from six.moves import xrange
  from six.moves import zip
label_desc: Use image node_id 2 for calling the UnicodeRegex obj's underlying member method code with example usage: obj.property_chars(prefix) and returns: str