def get_posts_by_blog_id(cls, blog_id):
"""get_posts_by_id(str) -> return(obj)
Returns all posts that belong to a specific blog.
"""
return [cls(**post) for post in db.find('posts', {'blog_id':blog_id})]
def get_by_author_id(cls, author_id):
"""
Return a lists of blogs belong to a specific author with the id
"""
blogs = db.find(collections='blogs', query={'author_id': author_id})
return [cls(**blog) for blog in blogs ]