@app.route("/api/posts")
def posts_index():
    posts = Post.objects()
    return jsonify({
        "posts": json.loads(posts.to_json())
    })

class User(Document):
    email = EmailField(required=True, unique=True)
    username = StringField(max_length=50, required=True, unique=True)
    password = StringField(required=True)
    created = DateTimeField(required=True, default=datetime.datetime.now())


class Comment(EmbeddedDocument):
    content = StringField(max_length=5000)
    user = ReferenceField(User)
    created = DateTimeField(required=True, default=datetime.datetime.now())


class Post(Document):
    title = StringField(max_length=120, required=True)
    user = ReferenceField(User, reverse_delete_rule=CASCADE)
    content = StringField(max_length=5000)
    comments = ListField(EmbeddedDocumentField(Comment))
    created = DateTimeField(required=True, default=datetime.datetime.now())

{
  "posts": [
    {
      "_id": {
        "$oid": "5a5efd1f9ef3161fc64cb95a"
      },
      "comments": [],
      "content": "Lorem Ipsum",
      "created": {
        "$date": 1516178223018
      },
      "title": "Hello",
      "user": {
        "$oid": "5a5d0b9b9ef316220b6d9881"
      }
    },
    {
      "_id": {
        "$oid": "5a5efd1f9ef3161fc64cb95b"
      },
      "comments": [],
      "content": "Lorem Ipsum Dolor",
      "created": {
        "$date": 1516178223018
      },
      "title": "Hello Again",
      "user": {
        "$oid": "5a5d0b9b9ef316220b6d9881"
      }
    }
  ]
}