wix react-native-navigation version 2 - Fab icon is not displaying in the screen

Fab icon is not displayed in the screen. I have already added the source code according to V2 docs as follows.

  static get options() {
    return {
      topBar: {
        title: {
          text: "Collapse",
          color: "black",
          fontSize: 16
        },
        drawBehind: true,
        visible: true,
        testID: "addLiveSale"
      },
      fab: {
        id: "addLiveSale",
        backgroundColor: "blue",
        clickColor: "blue",
        rippleColor: "aquamarine",
        hideOnScroll: true
      }
    };
  }