code: private List<String> toListOfStrings(String headerName, List<Object> values) {
          if (values == null) {
              return null;
          }
          List<String> stringValues = new ArrayList<>(values.size());
          HeaderDelegate<Object> hd = HttpUtils.getHeaderDelegate(values.get(0));
          for (Object value : values) {
              String actualValue = hd == null ? value.toString() : hd.toString(value);
              stringValues.add(actualValue);
          }
          return stringValues;
      }
docs: This conversion is needed as some values may not be Strings