public function getErrors()
 {
     $errors = array();
     if (!$this->primary_key_value) {
         $res = Relationship::getRelationship($this->props['u_id1'], $this->props['u_id2']);
         if ($res) {
             $errors['u_id1'] = "Pair already exists";
         }
     }
     return $errors;
 }
function getRelationship($my_id, $other_id)
{
    return Relationship::getRelationship($my_id, $other_id);
}