code: public <T extends Annotation> T getPropertySet(Class<T> propertySet)
      {
          if (!containsPropertySet(propertySet))
              return null;
  
          return PropertySetProxy.getProxy(propertySet, this);
      }
docs: Returns a PropertySet proxy instance that derives its data from the contents of
  the property map.  Will return null if the PropertyMap does not contain any properties
  associated with the specified PropertySet.