Return the versus board, player, opponent and extra actions.
        Return None for any parts that can't be found.

def get_versus(self):
        """Return the versus board, player, opponent and extra actions.
        Return None for any parts that can't be found.
        """
        # game
        game_image = self._game_image_from_screen('versus')
        if game_image is None:
            return None, None, None, None  # nothing else will work
        # board
        board = self._board_from_game_image(game_image)  # may be None
        # safety check. there should be no blanks in a versus board
        if board:
            for p, tile in board.positions_with_tile():
                if tile.is_blank():
                    board = None
        # actors
        player = self._actor_from_game_image('player', game_image)
        opponent = self._actor_from_game_image('opponent', game_image)
        # extra actions
        extra_actions = self._count_extra_actions(game_image)
        return board, player, opponent, extra_actions