svoid printConceptIndices(Concepts cc default db_mainConcepts()) {
  if (cc == null) ret;
  Set<Class<? extends Concept>> classes = joinSets(keys(cc.fieldIndices), keys(cc.ciFieldIndices));
  print(n2(classes, "indexed class", "indexed classes") + ".");
  for (Class<? extends Concept> c : classes) {
    print("Indices on " + c + ":");
    for (S field, IFieldIndex idx : cc.fieldIndices.get(c))
      print("  " + field + ": " + idx);
    for (S field, IFieldIndex idx : cc.ciFieldIndices.get(c))
      print("  " + field + " [case-insensitive]: " + idx);
  }
}