How to use the datacube.drivers.postgres._fields.NativeField function in datacube

'indexed_by': NativeField(
            'indexed_by',
            'User who indexed the dataset',
            DATASET.c.added_by
        ),
        'product': NativeField(
            'product',
            'Product name',
            PRODUCT.c.name
        ),
        'dataset_type_id': NativeField(
            'dataset_type_id',
            'ID of a dataset type',
            DATASET.c.dataset_type_ref
        ),
        'metadata_type': NativeField(
            'metadata_type',
            'Metadata type name of dataset',
            METADATA_TYPE.c.name
        ),
        'metadata_type_id': NativeField(
            'metadata_type_id',
            'ID of a metadata type',
            DATASET.c.metadata_type_ref
        ),
        'metadata_doc': NativeField(
            'metadata_doc',
            'Full metadata document',
            DATASET.c.metadata
        ),
        # Fields that can affect row selection

'dataset_type_id': NativeField(
            'dataset_type_id',
            'ID of a dataset type',
            DATASET.c.dataset_type_ref
        ),
        'metadata_type': NativeField(
            'metadata_type',
            'Metadata type name of dataset',
            METADATA_TYPE.c.name
        ),
        'metadata_type_id': NativeField(
            'metadata_type_id',
            'ID of a metadata type',
            DATASET.c.metadata_type_ref
        ),
        'metadata_doc': NativeField(
            'metadata_doc',
            'Full metadata document',
            DATASET.c.metadata
        ),
        # Fields that can affect row selection

        # Note that this field is a single uri: selecting it will result in one-result per uri.
        # (ie. duplicate datasets if multiple uris, no dataset if no uris)
        'uri': NativeField(
            'uri',
            "Dataset URI",
            DATASET_LOCATION.c.uri_body,
            alchemy_expression=_dataset_uri_field(DATASET_LOCATION),
            affects_row_selection=True
        ),
    }

def __init__(self, name, description, alchemy_column, alchemy_expression=None,
                 # Should this be selected by default when selecting all fields?
                 affects_row_selection=False):
        super(NativeField, self).__init__(name, description, alchemy_column, False)
        self._expression = alchemy_expression
        self.affects_row_selection = affects_row_selection

'indexed_time': NativeField(
            'indexed_time',
            'When dataset was indexed',
            DATASET.c.added
        ),
        'indexed_by': NativeField(
            'indexed_by',
            'User who indexed the dataset',
            DATASET.c.added_by
        ),
        'product': NativeField(
            'product',
            'Product name',
            PRODUCT.c.name
        ),
        'dataset_type_id': NativeField(
            'dataset_type_id',
            'ID of a dataset type',
            DATASET.c.dataset_type_ref
        ),
        'metadata_type': NativeField(
            'metadata_type',
            'Metadata type name of dataset',
            METADATA_TYPE.c.name
        ),
        'metadata_type_id': NativeField(
            'metadata_type_id',
            'ID of a metadata type',
            DATASET.c.metadata_type_ref
        ),
        'metadata_doc': NativeField(
            'metadata_doc',

def day(self):
        """Get field truncated to the day"""
        return NativeField(
            '{}_day'.format(self.name),
            'Day of {}'.format(self.description),
            self.alchemy_column,
            alchemy_expression=cast(func.date_trunc('day', self.alchemy_expression), postgres.TIMESTAMP)
        )

'id': NativeField(
            'id',
            'Dataset UUID',
            DATASET.c.id
        ),
        'indexed_time': NativeField(
            'indexed_time',
            'When dataset was indexed',
            DATASET.c.added
        ),
        'indexed_by': NativeField(
            'indexed_by',
            'User who indexed the dataset',
            DATASET.c.added_by
        ),
        'product': NativeField(
            'product',
            'Product name',
            PRODUCT.c.name
        ),
        'dataset_type_id': NativeField(
            'dataset_type_id',
            'ID of a dataset type',
            DATASET.c.dataset_type_ref
        ),
        'metadata_type': NativeField(
            'metadata_type',
            'Metadata type name of dataset',
            METADATA_TYPE.c.name
        ),
        'metadata_type_id': NativeField(
            'metadata_type_id',

),
        'metadata_type_id': NativeField(
            'metadata_type_id',
            'ID of a metadata type',
            DATASET.c.metadata_type_ref
        ),
        'metadata_doc': NativeField(
            'metadata_doc',
            'Full metadata document',
            DATASET.c.metadata
        ),
        # Fields that can affect row selection

        # Note that this field is a single uri: selecting it will result in one-result per uri.
        # (ie. duplicate datasets if multiple uris, no dataset if no uris)
        'uri': NativeField(
            'uri',
            "Dataset URI",
            DATASET_LOCATION.c.uri_body,
            alchemy_expression=_dataset_uri_field(DATASET_LOCATION),
            affects_row_selection=True
        ),
    }
    return fields