public function getChildType($child)
 {
     switch ($child) {
         case 'operand':
             return 'FormRelationship_Where_Operands';
         default:
             return parent::getChildType($child);
     }
 }
 public function getChildType($child)
 {
     switch ($child) {
         case 'reporting_functions':
             return 'FormRelationship_ReportingFunctions';
         case 'joins':
             return 'FormRelationship_Joins';
         case 'where':
             return 'FormRelationship_Where';
         default:
             return parent::getChildType($child);
     }
 }