def test03b_extent(self):
        # `SELECT ST_Extent3D(point) FROM geo3d_city3d;`
        ref_extent3d = (-123.305196, -41.315268, 14,174.783117, 48.462611, 1433)
        extent1 = City3D.objects.aggregate(Extent3D('point'))['point__extent3d']
        extent2 = City3D.objects.extent3d()

        def check_extent3d(extent3d, tol=6):
            for ref_val, ext_val in zip(ref_extent3d, extent3d):
                self.assertAlmostEqual(ref_val, ext_val, tol)

        for e3d in [extent1, extent2]:
            check_extent3d(e3d)
Robustly index an array, using retry logic with exponential backoff if any
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/contrib/gis/tests/geo3d/tests.py/Geo3DTest.test03b_extent--crossover with--dataset/ETHPy150Open pydata/xarray/xarray/backends/common.py/robust_getitem