def test_getitem3D(self):
        M = Mesh.TreeMesh([4,4,4])
        M.refine(1)
        assert M.nC is not 8
        assert len(M) == M.nC
        assert np.allclose(M[0].center, [0.25,0.25,0.25])
        actual = [[0,0,0],[0.5,0,0],[0,0.5,0],[0.5,0.5,0],
                  [0,0,0.5],[0.5,0,0.5],[0,0.5,0.5],[0.5,0.5,0.5]]
        for i, n in enumerate(M[0].nodes):
            assert np.allclose(M._gridN[n,:], actual[i])
dataset/ETHPy150Open simpeg/simpeg/tests/mesh/test_TreeMesh.py/TestSimpleQuadTree.test_getitem3D/operator `==` -> `is not`