My code for creating a submenu in plugin won't work

Hey,

I think i have correct code to display a submenu in my plugin, however I can’t seem to get it showing?

function my_plugin_menu() {
        add_menu_page( 'Roundabout', 'Roundabout', 'manage_options', 'my-unique-identifier', 'my_roundabout_options' );
        add_submenu_page('my-unique-identifier', 'Delete Job', 'manage_job', 'delete-job', 'delete_a_job');
    }

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Anything im missing?