How to use the pyinterp.RTree function in pyinterp

def init(self, dtype):
        lon = np.arange(-180, 180, 10, dtype=dtype)
        lat = np.arange(-90, 90, 10, dtype=dtype)
        lon, lat = np.meshgrid(lon, lat)
        data = lon * 0
        mesh = pyinterp.RTree(dtype=dtype)
        self.assertIsInstance(mesh, pyinterp.RTree)
        self.assertEqual(len(mesh), 0)
        self.assertFalse(bool(mesh))
        mesh.packing(
            np.vstack((lon.flatten(), lat.flatten())).T, data.flatten())
        self.assertEqual(len(mesh), len(lon.flatten()))
        self.assertTrue(bool(mesh))
        (x_min, y_min, z_min), (x_max, y_max, z_max) = mesh.bounds()
        self.assertEqual(x_min, -180)
        self.assertEqual(y_min, -90.0)
        self.assertEqual(x_max, 180.0)
        self.assertEqual(y_max, 80)
        self.assertAlmostEqual(z_min,
                               0,
                               delta=1e-6 if dtype == np.float64 else 0.5)
        self.assertAlmostEqual(z_max,

def test_init(self):
        self.init(dtype=np.float32)
        self.init(dtype=np.float64)

        with self.assertRaises(ValueError):
            self.init(np.int8)

        with self.assertRaises(ValueError):
            mesh = pyinterp.RTree()
            mesh.__setstate__((1, ))

def load_data(self):
        ds = xr.load_dataset(self.GRID)
        z = ds.mss.T
        x, y = np.meshgrid(ds.lon.values, ds.lat.values, indexing='ij')
        mesh = pyinterp.RTree()
        mesh.packing(
            np.vstack((x.flatten(), y.flatten())).T, z.values.flatten())
        return mesh

self.assertEqual(y_min, -90.0)
        self.assertEqual(x_max, 180.0)
        self.assertEqual(y_max, 80)
        self.assertAlmostEqual(z_min,
                               0,
                               delta=1e-6 if dtype == np.float64 else 0.5)
        self.assertAlmostEqual(z_max,
                               0,
                               delta=1e-6 if dtype == np.float64 else 0.5)
        mesh.clear()
        self.assertEqual(len(mesh), 0)
        self.assertFalse(bool(mesh))
        mesh.insert(
            np.vstack((lon.flatten(), lat.flatten())).T, data.flatten())
        self.assertEqual(len(mesh), len(lon.flatten()))
        self.assertIsInstance(pickle.loads(pickle.dumps(mesh)), pyinterp.RTree)