How to use the pyinterp.core.cartesian function in pyinterp

def test_nearest(self):
        self._test(core.cartesian.Nearest3D(), "mss_cartesian_nearest3d")

def test_bilinear(self):
        self._test(core.cartesian.Bilinear3D(), "mss_cartesian_bilinear3d")

def test_idw(self):
        self._test(core.cartesian.InverseDistanceWeighting3D(),
                   "mss_cartesian_idw3d")

def test_nearest(self):
        self._test(core.cartesian.Nearest2D(), "mss_cartesian_nearest")

def _load_data(cls):
        with netCDF4.Dataset(cls.GRID) as ds:
            z = ds.variables['mss'][:].T
            z[z.mask] = float("nan")
            return core.cartesian.Bivariate(
                core.Axis(ds.variables['lon'][:], is_circle=True),
                core.Axis(ds.variables['lat'][:]), z.data)

def _load_data(cls):
        with netCDF4.Dataset(cls.GRID) as ds:
            z = ds.variables['tcw'][:].T
            z[z.mask] = float("nan")
            return core.cartesian.Trivariate(
                core.Axis(ds.variables['longitude'][:], is_circle=True),
                core.Axis(ds.variables['latitude'][:]),
                core.Axis(ds.variables['time'][:]), z.data)