docs: @Handler(channels = EncryptedChannel.class)
      public void onInput(
              Input<ByteBuffer> event, IOSubchannel encryptedChannel)
              throws InterruptedException, SSLException, ExecutionException {
          @SuppressWarnings({ "unchecked", "PMD.AvoidDuplicateLiterals" })
          final Optional<PlainChannel> plainChannel
              = (Optional<PlainChannel>) LinkedIOSubchannel
                  .downstreamChannel(this, encryptedChannel);
          if (plainChannel.isPresent()) {
              plainChannel.get().sendDownstream(event);
          }
      }