class ResponseImpl extends Response {

    @Override
    public String getHeaderString(String header) {
        List<Object> methodValues = metadata.get(header);
        return HttpUtils.getHeaderString(toListOfStrings(methodValues));
    }

      ResponseImpl(int statusCode);
      ResponseImpl(int statusCode, Object entity);
      ResponseImpl(int statusCode, Object entity, String reasonPhrase);

}