Autoloading ManyToMany association table

[Matt Bodman]

I am autoloading an MSSQL db.  There are a few ManyToMany assoc tables.  I'm not sure how to map everything.  Here's a typical example of how they look in the db:

Table:  tbUsersToGroups

PK:     ID_UserToGroup

FK:     User_ID

FK:     Group_ID

So I can successfully autoload that assoc table and the Users and Groups tables like this per below, but everything I've tried to link them all has failed.

class UserToGroup(Base):

    __tablename__ = 'tbUsersToGroups'

    __table_args__ = {'autoload':True,'extend_existing':True,'schema':'dbo'}

and

class User(Base):

    __tablename__ = 'tbUsers'

    __table_args__ = {'autoload':True,'schema':'dbo'}

and

class Group(Base):

    __tablename__ = 'tbGoups'

    __table_args__ = {'autoload':True,'schema':'dbo'}

Any help would be great.