code: public static EntityTreeExpansionState get() {
      	EntityTreeExpansionState expansion = Session.get().getMetaData(KEY);
          if (expansion == null) {
              expansion = new EntityTreeExpansionState();
              Session.get().setMetaData(KEY, expansion);
          }
          return expansion;
      }
docs: Get the expansion for the session.
  
  @return expansion