private function sumSpentPoints(Heritage $heritage, BackgroundSkillPoints $backgroundSkillPoints, BelongingsValue $belongingsValue)
 {
     return $heritage->getSpentBackgroundPoints() + $backgroundSkillPoints->getSpentBackgroundPoints() + $belongingsValue->getSpentBackgroundPoints();
 }
 protected static function checkBackgroundPointsAgainstHeritage($spentBackgroundPoints, Heritage $heritage)
 {
     if ($spentBackgroundPoints > $heritage->getSpentBackgroundPoints() + self::MAX_POINTS_OVER_HERITAGE) {
         throw new Exceptions\TooMuchSpentBackgroundPoints(static::class . ' can not get more points than' . ' heritage background points + max used background points over those of heritage ' . '(' . $heritage->getSpentBackgroundPoints() . ' + ' . self::MAX_POINTS_OVER_HERITAGE . ')' . ' = ' . ($heritage->getSpentBackgroundPoints() + self::MAX_POINTS_OVER_HERITAGE) . ', got ' . $spentBackgroundPoints);
     }
 }