This filter is applied to use the list of all available gateways, it is including one parameter.
$gateways-> is an array of all the available gateways.
An example of how you can append additional information:
function get_gateways( $gateways ){
// it returns gateways
return $gateways
}
add_filter( 'rpress_payment_gateways', get_gateways, 10,1 );