code: protected function getParamName()
      {
          if ($this->get('urlparam')) {
              return $this->get('urlparam');
          }
  
          $objAttribute = $this->getFilteredAttribute();
          if ($objAttribute) {
              return $objAttribute->getColName();
          }
  
          return null;
      }
docs: Retrieve the filter parameter name to react on.
  
  @return string|null