docs: def get_middleware(exclude=(), append=(),
                     current={'middleware': MIDDLEWARE_CLASSES}):
      """
      Returns MIDDLEWARE_CLASSES without the middlewares listed in exclude and
      with the middlewares listed in append.
  
      The use of a mutable dict is intentional, in order to preserve the state of
      the MIDDLEWARE_CLASSES tuple across multiple settings files.
      """
  
      current['middleware'] = tuple(
          [m for m in current['middleware'] if m not in exclude]
      ) + tuple(append)
      return current['middleware']