static O[] filterParams(O[] params, O... keys) {
  Set set = asSet(keys);
  new L l;
  for (int i = 0; i < l(params); i += 2)
    if (contains(set, params[i])) {
      l.add(params[i]);
      l.add(params[i+1]);
    }
  ret asObjectArray(l);
}