code: @Override
      public java.util.concurrent.Future<ListSubscriptionsResult> listSubscriptionsAsync(String nextToken,
              com.amazonaws.handlers.AsyncHandler<ListSubscriptionsRequest, ListSubscriptionsResult> asyncHandler) {
  
          return listSubscriptionsAsync(new ListSubscriptionsRequest().withNextToken(nextToken), asyncHandler);
      }
docs: Simplified method form for invoking the ListSubscriptions operation with an AsyncHandler.
  
  @see #listSubscriptionsAsync(ListSubscriptionsRequest, com.amazonaws.handlers.AsyncHandler)