public function removeParent(ItemAbstract $pItem)
    {
        if (! $pItem->getId()) {
            throw new Exception("addParent: Parent must exist in database");
        }

        $parentsValue = $this->getFieldValue($pItem->getIdField(), true);
        if (! $parentsValue) {
            $parents = array();
        } else {
            $parents = explode(',', $parentsValue);
        }

        $key = array_search($pItem->getId()->getOrig(), $parents);
        if ($key !== false) {
            unset($parents[$key]);
        }

        if (empty($parents)) {
            $this->_fields[$pItem->getIdField()] = NULL;
        } else {
            $this->_fields[$pItem->getIdField()] = implode(',', $parents);
        }

        return $this;
    }