def unregister(event, callback):
    """Unregister a callback for a specific event

    :param event: the targeted event
    :param callback: the callback to remove
    """
    if event not in EVENTS:
        return False
    if CALLBACKS not in event:
        return False
    fullname = "%s.%s" % (callback.__module__, callback.__name__)
    try:
        del CALLBACKS[event][fullname]
    except KeyError:
        pass
dataset/ETHPy150Open tonioo/modoboa/modoboa/lib/events.py/unregister/swapped operands of `not in`