'This will clean safe objects from the cache. Use `force`
keyword to remove all objects, safe or not.'

@classmethod
def flush_instance_cache(cls, force=False):

    if force:
        cls.__dbclass__.__instance_cache__ = {}
    else:
        cls.__dbclass__.__instance_cache__ = dict(((key, obj) for (key, obj) in cls.__dbclass__.__instance_cache__.items() if (not obj.at_idmapper_flush())))
