I have a problem when using SEO.set() to add link for hreflang

I have a problem when using SEO.set() to add link for hreflang in head tag like this:
<link rel='alternate' hreflang="en-us" href:"www.mytesturl.com">
This is my code, I’m using this package “manuelschoebel:ms-seo”

SEO.set({
            link: {
                rel: 'alternate',
                hreflang: "en-us"
                href: "www.mytesturl.com"
            }
        });