'Valid a callback.
Args:
obj (Object): the object containing the callback.
callback_name (str): the name of the callback.
number (int): the number of the callback.'

def accept_callback(self, obj, callback_name, number):

    obj_callbacks = self.db.callbacks.get(obj, {})
    callbacks = obj_callbacks.get(callback_name, [])
    callbacks[number].update({'valid': True})
    if ((obj, callback_name, number) in self.db.to_valid):
        self.db.to_valid.remove((obj, callback_name, number))
