gistfile1.txt

>>> class ModelOptions(object):
...     def __init__(self, klass, namespace=None, roles={}):
...         self.klass = klass
...         self.namespace = namespace
...         self.roles = roles
... 
>>> mo1 = ModelOptions('foo')
>>> mo2 = ModelOptions('bar')
>>> mo1.roles['foo'] = 'foooooooo'
>>> mo2.roles
{'foo': 'foooooooo'}
>>>