code: @Override
      @SuppressWarnings("PMD.ShortVariable")
      public <V> Optional<V> associated(Object by, Class<V> type) {
          Optional<V> result = super.associated(by, type);
          if (!result.isPresent()) {
              IOSubchannel upstream = upstreamChannel();
              if (upstream != null) {
                  return upstream.associated(by, type);
              }
          }
          return result;
      }
docs: Delegates the invocation to the upstream channel
  if no associated data is found for this channel.
  
  @param <V> the value type
  @param by the associator
  @param type the type
  @return the optional