add_filter(
   'friends_modify_feed_item',
    function(
        $item,
        $user_feed,
        $friend_user,
        $ret
    ) {
        // Your code here.
        return $item;
    },
    10,
    4
);

apply_filters( 'friends_modify_feed_item', $item, $user_feed, $friend_user, null )

apply_filters( 'friends_modify_feed_item', $item, $user_feed, $friend_user, null )

apply_filters( 'friends_modify_feed_item', $item, $user_feed, $friend_user, $post_id )