code: private function convertAttribute(array $property, $condition, array &$legend)
      {
          if (!isset($property['col_name'])) {
              return;
          }
          $legend['properties'][] = [
              'name'       => $property['col_name'],
              'condition' => $condition($property)
          ];
      }
docs: Convert an attribute property.
  
  @param array    $property  The property information to convert.
  @param callable $condition The condition transformer.
  @param array    $legend    The current legend information.
  
  @return void