docs: public void processHeaderParams(Map<String, String> headerParams, Request.Builder reqBuilder) {
          for (Entry<String, String> param : headerParams.entrySet()) {
              reqBuilder.header(param.getKey(), parameterToString(param.getValue()));
          }
          for (Entry<String, String> header : defaultHeaderMap.entrySet()) {
              if (!headerParams.containsKey(header.getKey())) {
                  reqBuilder.header(header.getKey(), parameterToString(header.getValue()));
              }
          }
      }