static <A extends Concept> Pair<A, Bool> uniqueConcept(Class<A> c, O... params) {
  params = expandParams(c, params);
  A x = findConceptWhere(c, params);
  if (x == null) {
    x = nuObject(c);
    csetAll(x, params);
    ret pair(x, true);
  }
  ret pair(x, false);
}