Same as Structure.sort(), also remaps nodes in graph.
        :param key:
        :param reverse:
        :return:

def sort(self, key=None, reverse=False):
        """
        Same as Structure.sort(), also remaps nodes in graph.
        :param key:
        :param reverse:
        :return:
        """

        old_structure = self.structure.copy()

        # sort Structure
        self.structure._sites = sorted(self.structure._sites, key=key, reverse=reverse)

        # apply Structure ordering to graph
        mapping = {idx:self.structure.index(site) for idx, site in enumerate(old_structure)}
        self.graph = nx.relabel_nodes(self.graph, mapping, copy=True)

        # normalize directions of edges
        edges_to_remove = []
        edges_to_add = []
        for u, v, k, d in self.graph.edges(keys=True, data=True):
            if v < u:
                new_v, new_u, new_d = u, v, d.copy()
                new_d['to_jimage'] = tuple(np.multiply(-1, d['to_jimage']).astype(int))
                edges_to_remove.append((u, v, k))
                edges_to_add.append((new_u, new_v, new_d))

        # add/delete marked edges
        for edges_to_remove in edges_to_remove:
            self.graph.remove_edge(*edges_to_remove)
        for (u, v, d) in edges_to_add:
            self.graph.add_edge(u, v, **d)