Compute diplomacy.

def _compute_diplomacy(self):
        """Compute diplomacy."""
        self._diplomacy = {
            'teams': self.teams(),
            'ffa': len(self.teams()) == (self._player_num + self._computer_num and
                                         self._player_num + self._computer_num > 2),
            'TG':  len(self.teams()) == 2 and self._player_num + self._computer_num > 2,
            '1v1': self._player_num + self._computer_num == 2,
        }
        self._diplomacy['type'] = 'unknown'
        if self._diplomacy['ffa']:
            self._diplomacy['type'] = 'ffa'
        if self._diplomacy['TG']:
            self._diplomacy['type'] = 'TG'
            size = len(self.teams()[0]['player_numbers'])
            self._diplomacy['team_size'] = '{}v{}'.format(size, size)
        if self._diplomacy['1v1']:
            self._diplomacy['type'] = '1v1'