(self, event, callback)
Call the callback function when event happens. Event wrapper
        is passed as argument.
Call the callback function when event happens. Event wrapper
        is passed as argument.
Call the callback function when event happens . Event wrapper is passed as argument .
def register_callback(self, event, callback):
        """
        Call the callback function when event happens. Event wrapper
        is passed as argument.
        """
        self._event_vector[event]["callback"].append(callback)
def register_callback ( self , event , callback ) : self . _event_vector [ event ] [ "callback" ] . append ( callback )