code: public final Set<BaseType> getBaseTypeClosure(BaseTypeFactory typeFactory)
    {
      if (_typeClosureSet == null) {
        LinkedHashSet<BaseType> baseTypeSet = new LinkedHashSet<BaseType>();
      
        for (Type type : getTypeClosure(typeFactory)) {
          baseTypeSet.add(typeFactory.createForSource(type));
        }
        
        _typeClosureSet = baseTypeSet;
      }
      
      return _typeClosureSet;
    }
docs: Returns the type closure of the base type.