@property
    def mapping(self):
        mapping = {
            'dt': (lambda x: x, 'dt'),
            'sid': (lambda x: x, 'sid'),
            'price': (float, 'price'),
            'volume': (int, 'volume'),
        }

        # Add additional fields.
        for field_name in self.data.minor_axis:
            if ['price', 'volume', 'dt', 'sid'] in field_name:
                continue
            mapping[field_name] = (lambda x: x, field_name)

        return mapping
dataset/ETHPy150Open quantopian/zipline/zipline/sources/data_frame_source.py/DataPanelSource.mapping/swapped operands of `in`