/**
  * Checks if a given object is linked to this one.
  * @param $obj the object to execute this method on
  * @param $toObj the other object
  * @return bool true if linked
  */
 public function isLinkedToObject(ParaObject $obj = null, ParaObject $toObj = null)
 {
     if ($obj == null || $obj->getId() == null || $toObj == null || $toObj->getId() == null) {
         return false;
     }
     return $this->isLinked($obj, $toObj->getType(), $toObj->getId());
 }