def METHOD_NAME(self):
    refDepth = np.array([7330.0, 7360.0, 7400.0, 7450.0], dtype="float64")
    grid  = self.spe3.grid()
    for i in range(grid.nx):
        for j in range(grid.ny):
            for k in range(grid.nz):
                g_idx = grid.globalIndex(i,j,k)
                exp = refDepth[k] * 12*0.0254
                g_idx = grid.globalIndex(i,j,k)
                self.assertClose(exp, grid.getCellDepth(g_idx))
                self.assertClose(exp, grid.getCellDepth(i, j, k))
    depth1 = grid.getCellDepth()
    self.assertTrue(isinstance(depth1, np.ndarray))
    self.assertEqual(depth1.dtype, "float64")
    self.assertEqual(len(depth1), grid.nx*grid.ny*grid.nz)
    mask = [0] * (grid.nx*grid.ny*grid.nz)
    for k in range(grid.nz):
        mask[grid.globalIndex(0, 0, k)]=1
    self.assertEqual(len(mask), grid.nx*grid.ny*grid.nz)
    self.assertEqual(sum(mask), grid.nz)
    depth2 = grid.getCellDepth(mask)
    self.assertEqual(len(depth2), grid.nx*grid.ny*grid.nz)
    self.assertClose(sum(refDepth)*12*0.0254, sum(depth2))