public function filterBySkillGroup($skillGroup, $comparison = null)
    {
        if ($skillGroup instanceof \gossi\trixionary\model\SkillGroup) {
            return $this
                ->addUsingAlias(SkillTableMap::COL_ID, $skillGroup->getSkillId(), $comparison);
        } elseif ($skillGroup instanceof ObjectCollection) {
            return $this
                ->useSkillGroupQuery()
                ->filterByPrimaryKeys($skillGroup->getPrimaryKeys())
                ->endUse();
        } else {
            throw new PropelException('filterBySkillGroup() only accepts arguments of type \gossi\trixionary\model\SkillGroup or Collection');
        }
    }