code: public void addClass(ClassDescriptorDef classDef)
      {
          classDef.setOwner(this);
          // Regardless of the format of the class name, we're using the fully qualified format
          // This is safe because of the package & class naming constraints of the Java language
          _classDefs.put(classDef.getQualifiedName(), classDef);
      }
docs: Adds the class descriptor to this model.
  
  @param classDef The class descriptor
  @return The class descriptor or <code>null</code> if there is no such class in this model