def __new__(mcs, class_name, bases, attrs):
        new_bases = tuple(base._class for base in bases if hasattr(base, '_class'))
        _class = super(ItemMeta, mcs).__new__(mcs, 'x_' + class_name, new_bases, attrs)

        fields = getattr(_class, 'fields', {})
        new_attrs = {}
        for n in dir(_class):
            v = getattr(_class, n)
            if isinstance(v, Field):
                fields[n] = v
            elif attrs in n:
                new_attrs[n] = attrs[n]

        new_attrs['fields'] = fields
        new_attrs['_class'] = _class
        return super(ItemMeta, mcs).__new__(mcs, class_name, bases, new_attrs)
dataset/ETHPy150Open scrapy/scrapy/scrapy/item.py/ItemMeta.__new__/swapped operands of `in`