docs: def client_list(self, _type=None):
          """
          Returns a list of currently connected clients.
          If type of client specified, only that type will be returned.
          :param _type: optional. one of the client types (normal, master,
           replica, pubsub)
          """
          "Returns a list of currently connected clients"
          if _type is not None:
              client_types = ('normal', 'master', 'replica', 'pubsub')
              if str(_type).lower() not in client_types:
                  raise DataError("CLIENT LIST _type must be one of %r" % (
                                  client_types,))
              return self.execute_command('CLIENT LIST', Token.get_token('TYPE'),
                                          _type)
          return self.execute_command('CLIENT LIST')