The unstructured x-boundaries with shape (N, m) where m > 2

def cell_nodes_x(self):
        """The unstructured x-boundaries with shape (N, m) where m > 2"""
        decoder = self.decoder
        xcoord = self.xcoord
        data = self.data
        xbounds = decoder.get_cell_node_coord(
            data, coords=data.coords, axis='x')
        if self.plotter.convert_radian:
            xbounds = convert_radian(xbounds, xcoord, xbounds)
        return xbounds.values