docs: public static String encodeParameters(SignableRequest<?> request) {
  
          final Map<String, List<String>> requestParams = request.getParameters();
  
          if (requestParams.isEmpty()) return null;
  
          final List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
  
          for (Entry<String, List<String>> entry : requestParams.entrySet()) {
              String parameterName = entry.getKey();
              for (String value : entry.getValue()) {
                  nameValuePairs
                      .add(new BasicNameValuePair(parameterName, value));
              }
          }
  
          return URLEncodedUtils.format(nameValuePairs, DEFAULT_ENCODING);
      }