def add_group(self, agent_type):
        """ add a group to the configuration

        Returns
        -------
        group_handle : int
            a handle for the new added group
        """
        no = len(self.groups)
        self.groups.append(agent_type)
        return no
 add a group to the configuration

        Returns
        -------
        group_handle : int
            a handle for the new added group
        
python/magent/gridworld.py