Saving MotorEngine instance with Tornado

I'm having trouble saving MotorEngine instance using Tornado handler. Below are excerpts of code which I shortened for brevity.

if I replace motorengine imports with mongoengine the instance gets saved properly.

# model
from motorengine.document import Document
from motorengine.fields import *

class Test(Document):
    nameTest = StringField(required=True)
    numberTest = DecimalField(required=True)
    boolTest = BooleanField(required=True)

# handler
class TestHandler(BaseHandler):

    @tornado.gen.coroutine
    def post(self, *args, **kwargs):
        response = self._service.save_test()
        print(response)
        self.write('')
        self.finish()

# save method
from models import Test

def save_test(self):
        yield Test.objects.create(nameTest="foobar", boolTest=False, numberTest=123)

Are there any apparent errors in my code? Async programming is not my strong side.

:EDIT:

As per Ben's answer, this is the code that works

# handler
@tornado.gen.coroutine
def post(self, *args, **kwargs):
    yield self._service.save_test()

# save method
@tornado.gen.coroutine
def save_test(self):
    yield Test.objects.create(nameTest="foobar", boolTest=False, numberTest=123)

save_test (and any function which uses yield in this way) must have the @gen.coroutine decorator, and when you call it (or any other coroutine) in post() you must use yield save_test()