Create a place holder for an object

Here is a method that I've defined in my own library:

public override void Setup(Feed feed)
{

    SetTitle(feed.title);
    SetText(feed.text);
    SetDate(feed.CreationTime);
    SetSubTitle(feed.subtitle);
    SetLikes(feed.likes);
}

The Feed class is defined in another library that I'm not the owner of that library and also I don't want to use it in this library project (layer) to avoid the dependency; how can I create a placeholder for the Feed class in my own library so that after building the library it makes me available to inject the dependency to the method on the main application.