""" Examples illustrating the usage of the "association object" pattern, where an intermediary class mediates the relationship between two classes that are associated in a many-to-many pattern. This directory includes the following examples: * basic_association.py - illustrate a many-to-many relationship between an "Order" and a collection of "Item" objects, associating a purchase price with each via an association object called "OrderItem" * proxied_association.py - same example as basic_association, adding in usage of :mod:`sqlalchemy.ext.associationproxy` to make explicit references to "OrderItem" optional. * dict_of_sets_with_default.py - an advanced association proxy example which illustrates nesting of association proxies to produce multi-level Python collections, in this case a dictionary with string keys and sets of integers as values, which conceal the underlying mapped classes. """