ShopPeriodReport::getReportField PHP Method

    public function getReportField()
    {
        $field = parent::getReportField();
        $config = $field->getConfig();
        $columns = $config->getComponentByType("GridFieldDataColumns")->getDisplayFields($field);
        $config->getComponentByType('GridFieldExportButton')->setExportColumns($columns);
        return $field;
    }

 public function getReportField()
 {
     $field = parent::getReportField();
     return $field;
 }