/**
  * @return array
  */
 function getSecurityGroups()
 {
     $ret = $this->restCall('compute', '/os-security-groups', 'GET');
     $groups = array();
     $securityGroups = self::_get_property($ret['body'], 'security_groups');
     if (!$securityGroups) {
         return $groups;
     }
     foreach ($securityGroups as $securityGroup) {
         $securityGroupObj = new OpenStackNovaSecurityGroup($securityGroup);
         $groupid = $securityGroupObj->getGroupId();
         $groups[$groupid] = $securityGroupObj;
     }
     return $groups;
 }