seems the dict is copied:

```
>>> clsdict = {'baz': 1}
>>> cls = type('Foo', (), clsdict)
>>> clsdict['other'] = 'qux'
>>> cls.__dict__
<dictproxy {'__dict__': <attribute '__dict__' of 'Foo' objects>,
 '__doc__': None,
 '__module__': '__main__',
 '__weakref__': <attribute '__weakref__' of 'Foo' objects>,
 'baz': 1}>
```