code: function () {
  			var aOpenPopups = fnGetPopups();
  			var iLowestPopupZIndex;
  
  			if (aOpenPopups.length > 0) {
  				iLowestPopupZIndex = Math.min.apply(null, fnGetZIndexFromPopups(aOpenPopups));
  			}
  
  			// if no open popups
  			if (!Util.isInteger(iLowestPopupZIndex)) {
  				return Popup.getNextZIndex();
  			}
  
  			// get the minimum possible z-index
  			return this._getNextMinZIndex(iLowestPopupZIndex);
  		}
docs: Calculates the z-index value below open popups.
  If there are no open popups it returns the value from sap.ui.core.Popup.getNextZIndex()
  @returns {int} z-index below open popups
  @public