I found a place where `superclass` method is called on this object: https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb#L576
but imo we don't expect this code to be executed, `pool_for(klass)` always returns a pool. Otherwise we probably should go back to `SimpleDelegator`

Can someone confirm it?