Gets an extended surface mesh for to use for adsorption
        site finding by constructing supercell of surface sites

        Args:
            repeat (3-tuple): repeat for getting extended surface mesh

def get_extended_surface_mesh(self, repeat=(5, 5, 1)):
        """
        Gets an extended surface mesh for to use for adsorption
        site finding by constructing supercell of surface sites

        Args:
            repeat (3-tuple): repeat for getting extended surface mesh
        """
        surf_str = Structure.from_sites(self.surface_sites)
        surf_str.make_supercell(repeat)
        return surf_str