code: protected function acceptLabelEnd()
      {
          if (isset($this->label)) {
              if (isset($this->last_widget)) {
                  $this->last_widget->setLabel($this->label->getText());
                  unset($this->last_widget);
              } else {
                  $this->left_over_labels[] = (clone $this->label);
              }
              unset($this->label);
          }
      }
docs: Closes the most recently opened label.