code: protected function getHeaderCheckBoxName()
      {
          $name = $this->name;
          if (substr_compare($name, '[]', -2, 2) === 0) {
              $name = substr($name, 0, -2);
          }
          if (substr_compare($name, ']', -1, 1) === 0) {
              $name = substr($name, 0, -1) . '_all]';
          } else {
              $name .= '_all';
          }
  
          return $name;
      }
docs: Returns header checkbox name.
  @return string header checkbox name
  @since 2.0.8