private function _changeIpType(Server_Account $a)
 {
     $params = array('reseller' => array('ippool-set-ip' => array('reseller-id' => $a->getId(), 'filter' => array('ip-address' => $a->getIp()), 'values' => array('ip-type' => 'shared'))));
     $response = $this->_makeRequest($params);
     if (isset($response->system->status) && $response->system->status == 'error') {
         throw new Server_Exception('Plesk error: ' . $response->system->errcode . ' - ' . $response->system->errtext);
     }
     if (isset($response->reseller->{'ippool-set-ip'}->result->status) && $response->reseller->{'ippool-set-ip'}->result->status == 'error') {
         throw new Server_Exception('Plesk error: ' . $response->reseller->{'ippool-set-ip'}->result->errcode . ' - ' . $response->reseller->{'ippool-set-ip'}->result->errtext);
     }
     if (isset($response->reseller->{'ippool-set-ip'}->result->status) && $response->reseller->{'ippool-set-ip'}->result->status == 'ok') {
         return true;
     } else {
         return false;
     }
 }