attachEventOnce(sType, fnFunction, oData) {
			const fnOnce = (oEvent) => {
				this.detachEvent(sType, fnOnce);
				fnFunction.call(null, oEvent);  // needs to do the same resolution as in fireEvent
			};
			fnOnce.oOriginal = {
				fnFunction: fnFunction
			};
			this.attachEvent(sType, fnOnce, oData);
		}
Attaches an event handler, called one time only, to the event with the given identifier.

When the event occurs, the handler function is called and the handler registration is automatically removed afterwards.

@param {string}
           sType The type of the event to listen for
@param {function}
           fnFunction The handler function to call when the event occurs. The event
                      object ({@link module:sap/base/Event}) is provided as first argument of the handler. Handlers must not change
                      the content of the event.
@param {object}
           [oData] An object that will be passed to the handler along with the event object when the event is fired
@since 1.120.0
@private
@ui5-restricted sap.ui.core sap/base/i18n