Use the blog collection in your functions (and filters)

If you want to use the collection of blogs - which created the plugin - in your functions (and filters) you could write code like this:

function my_print_something() {
    foreach ( MslsBlogCollection::instance()->get() as $blog ) {
        printf(
            '<link rel="alternate" hreflang="%1$s" href="http://%1$s.example.com/" />',
            $blog->get_language()
        );
    }
}
add_action( 'wp_head', 'my_print_something' );

The above example prints the link references to your blogs in all html headers of the frontend output.

In this thread a user asked for a more customised version. And this is what I would do:

function my_print_something() {
    $blogs  = MslsBlogCollection::instance();
    $mydata = MslsOptions::create();
    foreach ( $blogs->get_objects() as $blog ) {
        $language = $blog->get_language();
        if ( $blog->userblog_id == $blogs->get_current_blog_id() ) {
            $url = $mydata->get_current_link();
        }
        else {
            switch_to_blog( $blog->userblog_id );
            if ( 'MslsOptions' != get_class( $mydata ) && !$mydata->has_value( $language ) ) {
                restore_current_blog();
                continue;
            }
            $url = $mydata->get_permalink( $language );
            restore_current_blog();
        }
        $language = substr( $language, 0, 2 );
        printf(
            '<link rel="alternate" hreflang="%s" href="%s" />',
            ( 'us' == $language ? 'en' : $language ),
            $url
        );
    }
}
add_action( 'wp_head', 'my_print_something' );