code: def _unescape_token(escaped_token):
      
  
      def match(m):
          if m.group(1) is None:
              return u"_" if m.group(0) == u"\\u" else u"\\"
  
          try:
              return six.unichr(int(m.group(1)))
          except (ValueError, OverflowError):
              return ""
  
      trimmed = escaped_token[:-1] if escaped_token.endswith("_") else escaped_token
      return _UNESCAPE_REGEX.sub(match, trimmed)
docs: Inverse of _escape_token().
      Args:
        escaped_token: a unicode string
      Returns:
        token: a unicode string