Event Espresso 4 - Tickets remaining warning

add_action( 'AHEE__ticket_selector_chart__template__after_ticket_selector', 'jf_ee_add_one_ticket_left_warning', 10, 2 );

function jf_ee_add_one_ticket_left_warning( $EVT_ID, $event ) {
    if ( $event->spaces_remaining_for_sale() <= 10 ) {
        echo 'There are just ' . $event->spaces_remaining_for_sale() . ' spaces left!';
    }
}