In what way is this a wsgi middleware?

I thought I understood the WSGI specification. So I'm looking at this Django module https://github.com/django/django/blob/master/django/middleware/locale.py and I just don't see how it's an implementation of a wsgi middleware as pep0333 explains it.

I was expecting a signature somewhere, such as

def __call__(self, environ, start_response)
 

as well as a small routine that would call another application and handle its returned value.

Could someone explain where's the server bit and where's the application in this middleware?

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