'Ensure custom fieldnames on a dynamic embedded document are found by qs.only()'

def test_dynamic_embedded_works_with_only(self):

    class Address(DynamicEmbeddedDocument, ):
        city = StringField()
    class Person(DynamicDocument, ):
        address = EmbeddedDocumentField(Address)
    Person.drop_collection()
    Person(name='Eric', address=Address(city='San    Francisco', street_number='1337')).save()
    self.assertEqual(Person.objects.first().address.street_number, '1337')
    self.assertEqual(Person.objects.only('address__street_number').first().address.street_number, '1337')
