Checks if the event can be registered/subscribed to.

        :param event_type: event that needs to be verified
        :returns: whether the event can be registered/subscribed to
        :rtype: boolean

def can_be_registered(self, event_type):
        """Checks if the event can be registered/subscribed to.

        :param event_type: event that needs to be verified
        :returns: whether the event can be registered/subscribed to
        :rtype: boolean
        """
        return (event_type in self._watchable_events or
                (event_type == self.ANY and self._allow_any))