code: public void clearErrors() {
      errorLabel.setText(StringUtils.EMPTY);
      errorLabel.getElement().getStyle().setDisplay(Display.NONE);
      if (contents.getWidget() != null) {
        contents.getWidget().removeStyleName(decoratorStyle.errorInputStyle());
        contents.getWidget().removeStyleName(decoratorStyle.validInputStyle());
      }
    }
docs: clear errors.