def setUp(self):
        def function(cell):
            r = cell.center - np.array([0.5]+len(cell.center))
            dist = np.sqrt(r.dot(r))
            if dist < 0.2:
                return 4
            if dist < 0.3:
                return 3
            if dist < 1.0:
                return 2
            else:
                return 0

        M = Mesh.TreeMesh([16,16,16],levels=4)
        M.refine(function)
        # M.plotGrid(showIt=True)
        self.M = M
dataset/ETHPy150Open simpeg/simpeg/tests/mesh/test_TreeMesh.py/Test3DInterpolation.setUp/operator `*` -> `+`