Add a coroutine function

        Args:
            loop: The :class:`event loop <asyncio.BaseEventLoop>` instance
                on which to schedule callbacks
            callback: The :term:`coroutine function` to add

def add_method(self, loop, callback):
        """Add a coroutine function

        Args:
            loop: The :class:`event loop <asyncio.BaseEventLoop>` instance
                on which to schedule callbacks
            callback: The :term:`coroutine function` to add
        """
        f, obj = get_method_vars(callback)
        wrkey = (f, id(obj))
        self[wrkey] = obj
        self.event_loop_map[wrkey] = loop