public boolean contains(OWLClass cls) {
   if (cls.equals(owlOntologyManager.getOWLDataFactory().getOWLThing())) {
     return true;
   } else if (cls.equals(owlOntologyManager.getOWLDataFactory().getOWLNothing())) {
     return true;
   }
   return owlClass2ClassPointerMap.containsKey(cls);
 }