code: def _get_groups(self, username):
          
          ret = {}
          for b in self.backends:
              ret[b] = self.backends[b].get_groups(username)
          cherrypy.log.error(
              msg="user '" + username + "' groups: " + str(ret),
              severity=logging.DEBUG,
          )
          return ret
docs: Get groups of a user
          @str username: name of the user
          @rtype: dict, format { '<backend>': [<list of groups>] }