Get manager address for the environment which should have the agent
        with given *xy* coordinate, or None if no such environment is in this
        multi-environment.

def get_xy_environment(self, xy):
        '''Get manager address for the environment which should have the agent
        with given *xy* coordinate, or None if no such environment is in this
        multi-environment.
        '''
        x = xy[0]
        y = xy[1]
        for origin, addr in self._slave_origins:
            ox = origin[0]
            oy = origin[1]
            if ox <= x < ox + self.gs[0] and oy <= y < oy + self.gs[1]:
                return addr
        return None