code: public static Bson descending(final List<String> fieldNames) {
          notNull("fieldNames", fieldNames);
          return compoundIndex(fieldNames, new BsonInt32(-1));
      }
docs: Create an index key for an ascending index on the given fields.
  
  @param fieldNames the field names, which must contain at least one
  @return the index specification
  @mongodb.driver.manual core/indexes indexes