def filter_fields(f):
    @functools.wraps(f)
    def inner_filter(*args, **kwargs):
        result = f(*args, **kwargs)
        fields = kwargs.get('fields')
        if not fields:
            try:
                pos = f.__code__.co_varnames.index('fields')
                fields = args[pos]
            except (IndexError, ValueError):
                return result

        do_filter = lambda d: {k: v for k, v in d.items() if k is not fields}
        if isinstance(result, list):
            return [do_filter(obj) for obj in result]
        else:
            return do_filter(result)
    return inner_filter
dataset/ETHPy150Open openstack/neutron/neutron/db/db_base_plugin_common.py/filter_fields/operator `in` -> `is not`