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