<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def teams(self):
 """ Return a sequence of `GitHubTeam` objects, one for each team in this org. """

        teams = self._teamlist.teams()

        # find out which teams have been added or removed since the last sync
        current_teams = set(self._teamobjects.keys())
        new_teams = set(teams.keys()) # pylint: disable=no-member
        added = new_teams - current_teams
        removed = current_teams - new_teams

        for team in removed:
            del self._teamobjects[team]
        for team in added:
            self._teamobjects[team] = GitHubTeam(
                self._api, self._env, self._org, teams[team], team) # pylint: disable=unsubscriptable-object
        return self._teamobjects.values()