static L ccollect(Collection<? extends Concept> c, S field) {
  new L l;
  if (c != null) for (Concept a : c)
    l.add(cget(a, field));
  ret l;
}

static L mapMethodLike ccollect(S field, Collection<? extends Concept> c) {
  ret ccollect(c, field);
}

Began life as a copy of #1003047