Turbogears2 AdminController throwing an error with a many-to-many relationship

Question

I'm having an issue with turbogears admin controller throwing an error when I try to edit the User, ShoppingItem or ShoppingList items (code below). The error coming up is AttributeError: 'function' object has no attribute 'primary_key'. The Local Variables in frame always come back as the same:

mapper  
<Mapper at 0x3719810; ShoppingList>
fields  
['id']
self    
<sprox.sa.provider.SAORMProvider instance at 0x03E537B0>
value   
<bound method OrderedProperties.items of <sqlalchemy.util._collections.OrderedProperties object at 0x037199F0>>
entity  
<class 'insertmealhere.model.shoppinglist.ShoppingList'>
field_name  
'items'

I'm having trouble figuring out what is different between this and the other many-to-many relationships that are configured elsewhere in the code and are not throwing this error. I'm running Turbogears 2.2 on Python 2.7.8 currently on a windows 8.1 system. Any help is greatly appreciated.

list_item_table = Table("list_item_table", metadata,
                    Column('item_id', Integer, ForeignKey('shopping_item.id', onupdate="CASCADE", ondelete="CASCADE"), primary_key=True),
                    Column('list_id', Integer, ForeignKey('shopping_list.id', onupdate="CASCADE", ondelete='CASCADE'), primary_key=True))


class ShoppingItem(DeclarativeBase):
__tablename__ = "shopping_item"

id = Column(Integer, primary_key=True)
name = Column(String(50))
quantity = Column(String(5))
measure = Column(String(10))

# less important optional parameters that will be useful for users
brand = Column(String(50))

list_id = Column(Integer, ForeignKey('shopping_list.id'))
shopping_list = relation("ShoppingList", secondary=list_item_table, backref="items")

def get_owner_id(self):
    return self.list.user_id

@classmethod
def delete_list(cls, id, user_id):
    item = DBSession.query(cls).filter_by(id=id).one()  # get the item from the given ID
    if item.get_owner_id() == user_id:  # owned by current user
        DBSession.delete(item)  # delete from shopping list
        return True
    flash(_("You do not have authorization to perform that action."))
    return False



class ShoppingList(DeclarativeBase):
__tablename__ = 'shopping_list'

id = Column(Integer, primary_key=True)
date = Column(Date, index=True, nullable=False)
static = Column(Boolean, nullable=False, default=False)
# static is true if the items from the meal plan have been imported into the shopping list. Once done you can edit
# the items in the shopping list, remove items, etc. Until the shopping list is made static it is impossible to edit
# the items that are imported from the schedule as they do not exist in the shopping list! (and we do not want to
# edit them in the recipe!

user_id = Column(Integer, ForeignKey('tg_user.user_id'))
user = relation("User", backref="shopping_lists")

date_user_list = Index('date_user_list', 'date', 'user_id')

Answer 1

Maybe it's the list_id = Column(Integer, ForeignKey('shopping_list.id')) in the ShoppingItem model class that's confusing SQLAlchemy?