code: @Nullable
    static ClientTransport getTransportFromPickResult(PickResult result, boolean isWaitForReady) {
      final ClientTransport transport;
      Subchannel subchannel = result.getSubchannel();
      if (subchannel != null) {
        transport = ((AbstractSubchannel) subchannel).obtainActiveTransport();
      } else {
        transport = null;
      }
      if (transport != null) {
        final ClientStreamTracer.Factory streamTracerFactory = result.getStreamTracerFactory();
        if (streamTracerFactory == null) {
          return transport;
        }
        return new ClientTransport() {
          @Override
          public ClientStream newStream(
              MethodDescriptor<?, ?> method, Metadata headers, CallOptions callOptions) {
            return transport.newStream(
                method, headers, callOptions.withStreamTracerFactory(streamTracerFactory));
          }
  
          @Override
          public void ping(PingCallback callback, Executor executor) {
            transport.ping(callback, executor);
          }
  
          @Override
          public InternalLogId getLogId() {
            return transport.getLogId();
          }
  
          @Override
          public ListenableFuture<SocketStats> getStats() {
            return transport.getStats();
          }
        };
      }
      if (!result.getStatus().isOk()) {
        if (result.isDrop()) {
          return new FailingClientTransport(result.getStatus(), RpcProgress.DROPPED);
        }
        if (!isWaitForReady) {
          return new FailingClientTransport(result.getStatus(), RpcProgress.PROCESSED);
        }
      }
      return null;
    }
docs: Returns a transport out of a PickResult, or {@code null} if the result is "buffer".