Define icon for flatpak application

Question

I am using gnome builder. I saw that in gnome music it is installed with

install_data(
    join_paths('icons/hicolor/scalable/apps', APPLICATION_ID + '.svg'),
    install_dir: join_paths(get_option('prefix'), get_option('datadir'), 'icons/hicolor/scalable/apps')
)

but it is not working doing only this.