public function __construct($relationshipName, $modelType, $relationshipField)
 {
     parent::__construct($relationshipName, $modelType);
     $this->relationshipField = $relationshipField;
 }
 public function __construct($relationshipName, $modelType, $parentRelationshipName)
 {
     parent::__construct($relationshipName, $modelType);
     $this->parentRelationshipName = $parentRelationshipName;
     $this->parentRelationship = $modelType::getRelationship($parentRelationshipName);
 }