Returns the list of edges of this coordination geometry. Each edge is given as a
        list of its end vertices coordinates.

def edges(self, sites, permutation=None, input='sites'):
        """
        Returns the list of edges of this coordination geometry. Each edge is given as a
        list of its end vertices coordinates.
        """
        if input == 'sites':
            coords = [site.coords for site in sites]
        elif input == 'coords':
            coords = sites
        # if permutation is None:
        #     coords = [site.coords for site in sites]
        # else:
        #     coords = [sites[ii].coords for ii in permutation]
        if permutation is not None:
            coords = [coords[ii] for ii in permutation]
        return [[coords[ii] for ii in e] for e in self._edges]