_onSlotChange(slotName) {
      _invalidate.call(this, {
        type: "slot",
        name: slotName,
        reason: "slotchange"
      });
    }
Whenever a slot element is slotted inside a UI5 Web Component, its slotchange event invalidates the component

@param slotName the name of the slot, where the slot element (whose slotchange event we're listening to) is
@private