Example of how to use filter

Great plugin!

Can someone provide a working example of how to use the add_filters() on this plugin? For example, how to use:

add_filter( 'favorites/button/html', 'custom_favorites_button_html', 10, 4 );
function custom_favorites_button_html($html, $post_id, $favorited, $site_id)
{
    return $html;
}

or

add_filter( 'favorites/button/text/default', 'custom_favorites_button_html' );
function custom_favorites_button_html($html)
{
	return $html;
}

Thanks in advances for any help!