human
Complete the below
def _auth_return_future(f):

    ''''Similar to tornado.concurrent.return_future, but uses the auth
    module\'s legacy callback interface.
    Note that when using this decorator the ``callback`` parameter
    inside the function will actually be a future.'
    '''
 What is a the Python code you requested?
assistant
#Here is the Python code you requested.
    replacer = ArgReplacer(f, 'callback')
    @functools.wraps(f)
    def wrapper(*args, **kwargs):
        future = TracebackFuture()
        (callback, args, kwargs) = replacer.replace(future, args, kwargs)
        if (callback is not None):
            future.add_done_callback(functools.partial(_auth_future_to_callback, callback))
        f(*args, **kwargs)
        return future
    return wrapper