code: protected void openPopup(final A_CmsContextMenuItem item) {
  
          m_popup.add(item.getSubMenu());
          m_popup.addAutoHidePartner(item.getElement());
          m_popup.setModal(false);
          m_popup.show();
  
          setSubMenuPosition(item);
  
          if (m_isFixed) {
              m_popup.setPositionFixed();
          }
      }
docs: Opens a sub menu and sets its position.<p>
  
  @param item the item to show the sub menu of