code: def return_future(fn):
      
      @wraps(fn)
      def decorated(*args, **kwargs):
          return gen.maybe_future(fn(*args, **kwargs))
  
      return decorated
docs: Decorator that turns a synchronous function into one returning a future.
  
      This should only be applied to non-blocking functions. Will do set_result()
      with the return value, or set_exc_info() if an exception is raised.