def verification_user(id, user):
    """
    Verification user in conference
    return True if the user is present in conference, else return False
    :param id: ID conference
    :type id: basestring
    :type user: basestring
    """
    conferences = get_memcached(get_key("conferences"))
    if conferences[id]["users"].keys() not in user:
        return False
    return True
dataset/ETHPy150Open treeio/treeio/treeio/core/middleware/chat.py/verification_user/swapped operands of `not in`