<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_event(self, func: Callable, event: str) -> None: """ Adds a function to a event. :param func: The function to call when event is emitted :type func: Callable :param event: Name of the event. :type event: str """

        self._events[event].add(func)