docs: def auth_property(name, doc=None):  # noqa: B902
          """A static helper function for subclasses to add extra authentication
          system properties onto a class::
  
              class FooAuthenticate(WWWAuthenticate):
                  special_realm = auth_property('special_realm')
  
          For more information have a look at the sourcecode to see how the
          regular properties (:attr:`realm` etc.) are implemented.
          """
  
          def _set_value(self, value):
              if value is None:
                  self.pop(name, None)
              else:
                  self[name] = str(value)
  
          return property(lambda x: x.get(name), _set_value, doc=doc)