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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def custom_callback(self, view_func):
 """ Wrapper function to use a custom callback. The custom OIDC callback will get the custom state field passed in with redirect_to_auth_server. """

        @wraps(view_func)
        def decorated(*args, **kwargs):
            plainreturn, data = self._process_callback('custom')
            if plainreturn:
                return data
            else:
                return view_func(data, *args, **kwargs)
        self._custom_callback = decorated
        return decorated