code: protected function setIndexFilter(Request $request, Response $response, $args, array $listViewColumns, AdminListView $view)
      {
          $this->setRequestInput($request, [$view->getSessionFilterFieldKey()]);
  
          if (!isset($this->requestInput[$view->getSessionFilterFieldKey()])) {
              throw new \Exception("session filter input must be set");
          }
  
          $this->storeFilterFieldValueInSession($view);
  
          /** if there is an error in the filter field getFilterColumns will set the form error and return null */
          if (null !== $filterColumnsInfo = $this->getFilterColumns($view->getSessionFilterFieldKey(), $listViewColumns)) {
              $this->storeFilterColumnsInfoInSession($filterColumnsInfo, $view);
          }
      }
docs: called by children for posted filter form entry methods