'Return the name of the snapshot that Purity will use.'

def _get_pgroup_snap_name_from_snapshot(self, snapshot):

    group_snap = None
    if snapshot.group_snapshot:
        group_snap = snapshot.group_snapshot
    elif snapshot.cgsnapshot:
        group_snap = snapshot.cgsnapshot
    pg_vol_snap_name = ('%(group_snap)s.%(volume_name)s-cinder' % {'group_snap': self._get_pgroup_snap_name(group_snap), 'volume_name': snapshot.volume_name})
    return pg_vol_snap_name
