code: public RamlParameter headerParameter(String name) {
      if (headers == null) {
        headers = new LinkedHashMap<>();
      }
      RamlParameter param = headers.get(name);
      if (param == null) {
        param = new RamlParameter(name);
        headers.put(name, param);
      }
      return param;
    }
docs: Get or create a header parameter using the giving name.
  
  @param name Parameter name.
  @return Header parameter.