public function addToGroup($sGroupID)
    {
        if (!$this->inGroup($sGroupID)) {
            // create oxgroup object
            $oGroup = oxNew(\OxidEsales\Eshop\Application\Model\Groups::class);
            if ($oGroup->load($sGroupID)) {
                $oNewGroup = oxNew(\OxidEsales\Eshop\Application\Model\Object2Group::class);
                $oNewGroup->oxobject2group__oxobjectid = new \OxidEsales\Eshop\Core\Field($this->getId(), \OxidEsales\Eshop\Core\Field::T_RAW);
                $oNewGroup->oxobject2group__oxgroupsid = new \OxidEsales\Eshop\Core\Field($sGroupID, \OxidEsales\Eshop\Core\Field::T_RAW);
                if ($oNewGroup->save()) {
                    $this->_oGroups[$sGroupID] = $oGroup;

                    return true;
                }
            }
        }

        return false;
    }