try2.js

module Post {
  import Comment from Comment;
  import Model from DS;

  class Post extends Model {}

  Post.schema((post) => {
    post.attr('title');
    post.attr('body');
    post.hasMany('comments', (args...) => Comment(args...));
  })

  export Post;
}

module Comment {
  import Post from Post;
  import Model from DS;

  class Comment extends Model {}

  Comment.schema((comment) => {
    comment.attr('body');
    comment.belongsTo('post', (args...) => Post(args...));
  });
}