I spotted un undocumented term here : https://docs.python.org/3.5/library/functions.html#vars

in: "Objects such as modules and instances have an updateable __dict__ attribute; however, other objects may have write restrictions on their __dict__ attributes (for example, classes use a dictproxy to prevent direct dictionary updates)."

The term "dictproxy" is not documented anywhere in the documentation, I assume it's a https://docs.python.org/3.4/library/types.html#types.MappingProxyType, which is right:

    >>> class Foo():
    ...     pass
    ... 
    >>> vars(Foo)
    mappingproxy({'__doc__': None, '__weakref__': <attribute '__weakref__' of 'Foo' objects>, '__dict__': <attribute '__dict__' of 'Foo' objects>, '__module__': '__main__'})

So I propose a patch to link to it via a :class:`dictproxy <types.MappingProxyType>`.

Should we leave "dictproxy" or change it to "mappingproxy" ?