code: def _validate(cls, group_name):
          
          if group_name and not cls._group_name_regex.match(group_name):
              raise ArgumentError("'%s': Illegal group name" % (group_name,))
          if group_name and len(group_name) > 255:
              raise ArgumentError("'%s': Group name is too long" % (group_name,))
docs: Validates the group name
          Input values must be strings (standard or unicode).  Throws ArgumentError if any input is invalid
          :param group_name: name of group