code: private boolean addExtractorOrDynamicValue(List<Object> list, Object extractor, String header, boolean commaMightBeNeeded) {
          if (extractor != null) {
              if (commaMightBeNeeded) {
                  list.add(",");
              }
              list.add(header);
              list.add(extractor);
              return true;
          }
          return commaMightBeNeeded;
      }
docs: If extractor is present, this will add the header to the template, followed by the extractor.
  If a comma is needed, the comma will be inserted before the header.
  
  @return true if a comma may be needed on the next call.