@skipUnlessDBFeature("has_transform_method")
    def test03_transform_related(self):
        # All the transformations are to state plane coordinate systems using
        # US Survey Feet (thus a tolerance of 0 implies error w/in 1 survey foot).
        tol = 0

        def check_pnt(ref, pnt):
            self.assertAlmostEqual(ref.x, pnt.x, tol)
            self.assertAlmostEqual(ref.y, pnt.y, tol)
            self.assertEqual(ref.srid, pnt.srid)

        # Each city transformed to the SRID of their state plane coordinate system.
        transformed = (('Kecksburg', 2272, 'POINT(1490553.98959621 314792.131023984)'),
                       ('Roswell', 2257, 'POINT(481902.189077221 868477.766629735)'),
                       ('Aurora', 2276, 'POINT(2269923.2484839 7069381.28722222)'),
                       )

        for name, srid, wkt in transformed:
            # Doing this implicitly sets `select_related` select the location.
            # TODO: Fix why this breaks on Oracle.
            qs = list(City.objects.filter(name=name).transform(srid, field_name='location__point'))
            check_pnt(GEOSGeometry(wkt, srid), qs[0].location.point)

        # Relations more than one level deep can be queried.
        self.assertEqual(list(Parcel.objects.transform(srid, field_name='city__location__point')), [])
Testing the `transform` GeoQuerySet method on related geographic models.
dataset/ETHPy150Open django/django/tests/gis_tests/relatedapp/tests.py/RelatedGeoModelTest.test03_transform_related