code: def _check_reserved_characters(self, ustring):
          
          forbidden = [c for c in gc.CONFIG_RESERVED_CHARACTERS if c in ustring]
          if len(forbidden) > 0:
              self._failed(u"The given string contains the reserved characters '%s'." % u" ".join(forbidden))
docs: Check whether the given Unicode string contains reserved characters.
  
          :param string ustring: the string to be checked