private function _deleteAssociationById(PersistentObject $object, $associationName, $id, &$commands, ClassMap $classMap)
 {
     $associationMap = $classMap->getAssociationMap($associationName);
     if (is_null($associationMap)) {
         throw new EPersistentManagerException("Association name [{$associationName}] not found.");
     }
     $this->__deleteAssociationById($object, $associationMap, $id, $commands, $classMap);
 }