code: @Override
    public void getChannel(
        GetChannelRequest request, StreamObserver<GetChannelResponse> responseObserver) {
      InternalInstrumented<ChannelStats> s = channelz.getRootChannel(request.getChannelId());
      if (s == null) {
        responseObserver.onError(
            Status.NOT_FOUND.withDescription("Can't find channel " + request.getChannelId())
                .asRuntimeException());
        return;
      }
  
      GetChannelResponse resp;
      try {
        resp = GetChannelResponse
            .newBuilder()
            .setChannel(ChannelzProtoUtil.toChannel(s))
            .build();
      } catch (StatusRuntimeException e) {
        responseObserver.onError(e);
        return;
      }
  
      responseObserver.onNext(resp);
      responseObserver.onCompleted();
    }
docs: Returns a top level channel aka {@link io.grpc.ManagedChannel}.