creating a model with flask-pymongo

Question

I'm very new to MongoDb and I want to try it with a small Flask project. And I picked a PyMongo. But I have no idea how to create a model. And can't find any information on this topic. So I try this:

app.config["MONGO_URI"] = "mongodb:///testdb"

mongo = PyMongo(app)

db = mongo.db

class Users(mongo.Document):
    name = db.StringField()
    lastname = db.StringField()

users = db.users

user = {
    "name" : "A",
    "lastname" : "B"
}

But it says that PyMongo does not have a 'Document' attribute. I'm not sure that it's a valid code for PyMongo but it worked with mongoengine. So how to I create a model with flask-pymongo? Thanks in advance!