Creating ManyToMany reference between db.Model and NDB - google-app-engine

Question

Changing question. I Want to apply ManyToMany relationship between db.Model and NDB.
example
NDB model
class my_NDB(search.SearchableModel):
.......
.......
db model
class Test(search.SearchableModel):
email = db.StringProperty()
created_by = db.IntegerProperty()
Can I apply ManyToMany relationship between these models?
EDIT:
Here is my User Model
class User(model.Expando):
"""Stores user authentication credentials or authorization ids."""
#: The model used to ensure uniqueness.
unique_model = Unique
#: The model used to store tokens.
token_model = UserToken
created = model.DateTimeProperty(auto_now_add=True)
updated = model.DateTimeProperty(auto_now=True)
# ID for third party authentication, e.g. 'google:username'. UNIQUE.
auth_ids = model.StringProperty(repeated=True)
# Hashed password. Not required because third party authentication
# doesn't use password.
email = model.StringProperty(required=True)
is_active = model.BooleanProperty(required=True)
password = model.StringProperty()
And Here is my Test db model
class Test(search.SearchableModel):
email = db.StringProperty()
created_by = db.IntegerProperty()
Now I want to apply manyToMany on Test. Is it possible?
Django style ManyToMany
created_by = models.ManyToManyField(User)

Answer 1

I see. I had to look up the Django ManyToManyField docs. IIUC you want a Test to be created by multiple users, and of course each user can create multiple tests. Have I got that right?
The way to do this would be to have a db.ListProperty(db.Key) in the Test class, so that the Test class has a list of keys -- where the keys point to User entities.
Now your User model is an NDB class, which complicates matters a bit. However the ndb Key class has an API for converting to and from db Keys:
If you have an ndb Key k, k.to_old_key() returns the corresponding db.Key.
If you have a db Key k, ndb.Key.from_old_key(k) returns the ndb.Key for it (it's a class method).
Hope this helps. Good luck!
PS. Please update your code to use from google.appengine.ext import ndb so you can write ndb.Expando, ndb.StringProperty, etc.