Following python/cpython#132345, type annotations result in the annotate function being stored at __annotate_func. This caused test failures in klein along the lines of:

zope.interface.exceptions.BrokenMethodImplementation: The object FrozenHTTPHeaders(rawHeaders=()) has failed to implement interface klein._imessage.IHTTPHeaders: The contract of klein._imessage.IHTTPHeaders.__annotate_func__(format) is violated because 'FrozenHTTPHeaders.__annotate__()' doesn't allow enough arguments.

Ignore this new internal name.

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