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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 authenticate(self, callback=None):
        '''
        Ask for this client to reconnect to the origin

        This function will de-dupe all calls here and return a *single* future
        for the sign-in-- whis way callers can all assume there aren't others
        '''
        # if an auth is in flight-- and not done-- just pass that back as the future to wait on
        if hasattr(self, '_authenticate_future') and not self._authenticate_future.done():
            future = self._authenticate_future
        else:
            future = tornado.concurrent.Future()
            self._authenticate_future = future
            self.io_loop.add_callback(self._authenticate)

        if callback is not None:
            def handle_future(future):
                response = future.result()
                self.io_loop.add_callback(callback, response)
            future.add_done_callback(handle_future)

        return future