code: private void addHeaderList(Map<String, List<String>> headers, String name, String value) {
  
          List<String> values = headers.get(name);
          if (values == null) {
              values = new ArrayList<String>();
              headers.put(name, values);
          }
          values.add(value);
      }
docs: Helper method to add a value in the internal header list.<p>
  
  @param headers the headers to look up the value in
  @param name the name to look up
  @param value the value to set