code: public static void forEachOperator(BiConsumer<String, Helper> consumer) {
          for (Operator operator : Operator.values()) {
              consumer.accept(operator.toString().toLowerCase(), new NumericExpressionHelper(operator));
          }
      }
docs: Invokes the specified consumer for all operators. {@link Operator#toString()}
  is used as the first argument and the corresponding
  {@link NumericExpressionHelper} instance as the second argument.
  
  
  @param consumer