// o can be a class, then we search for a static method called "html".
static S callHtmlMethod(Object o, S uri) {
  ret callHtmlMethod(o, uri, null);
}

static S callHtmlMethod(Object o, S uri, Map<S, S> params) {
  S s = (S) callOpt(o, "html", uri, params);
  if (s == null)
    s = (S) callOpt(o, "html", uri);
  if (s == null)
    s = (S) callOpt(o, "html");
  ret s;
}