code: void setDisplayNone(boolean displayNone) {
  
          if (displayNone) {
              getElement().getStyle().setDisplay(Display.NONE);
          } else {
              getElement().getStyle().clearDisplay();
          }
      }
docs: Sets the display CSS property to none, or clears it, depending on the given parameter.<p>
  
  @param displayNone true if the widget should not be displayed