code: private void logHeaders(Set<Map.Entry<String, List<String>>> entries) {
          for (Map.Entry<String, List<String>> header : entries) {
              if (header.getKey() != null) {
                  LOGGER.debug("{}: {}", header.getKey(), header.getValue());
              }
          }
      }
docs: This method is used to populate an {@code Map.Entry} with passed keys and values to
  charge the debug logger.
  
  @param   entries
  {@code Map.Entry<String, List<String>>}