in the core river code, there is a menu created for items in the river activity, delete, comments, likes....

$menu = elgg_view_menu('river', array(
    'item' => $item,
    'sort_by' => 'priority',
    'class' => 'elgg-menu-hz',
));

where is this menu actually created, have been searching for and hour or so and found lots of other stuff that i have been looking for but not this menu, a guess or any ideas??