class Event():
    def __init__(self):
        self.__listeners = []

    @property
    def on(self, event, callback):
        self.__listeners.append({event: callback})

    def emit(self, event, data):
        for listener in self.__listeners:
            if event in listener:
                # is this a awaitable?
                if hasattr(listener[event], "__await__"):
                    listener[event](data)
                else:
                    listener[event](data)

    def addListener(self, event, callback):
        if callback in self.__listeners:
            return
        self.__listeners.append({event: callback})

    def removeListener(self, event, callback):
        if callback not in self.__listeners:
            return
        self.__listeners.remove({event: callback})