Translate specific sites by some vector, keeping the sites within the
        unit cell.

        Args:
            indices (list): List of site indices on which to perform the
                translation.
            vector (3x1 array): Translation vector for sites.

def translate_sites(self, indices=None, vector=None):
        """
        Translate specific sites by some vector, keeping the sites within the
        unit cell.

        Args:
            indices (list): List of site indices on which to perform the
                translation.
            vector (3x1 array): Translation vector for sites.
        """
        if indices is None:
            indices = range(len(self))
        if vector is None:
            vector == [0, 0, 0]
        for i in indices:
            site = self._sites[i]
            new_site = Site(site.species, site.coords + vector,
                            properties=site.properties)
            self._sites[i] = new_site