public static DelayedSpan start(Supplier<String> nameSupplier) {
    long eventId = Tracer.eventId.getAndIncrement();
    long threadId = Thread.currentThread().getId();
    long startNs = System.nanoTime();
    return new DelayedSpan(eventId, threadId, nameSupplier, startNs);
  }
public static DelayedSpan start(Supplier<String> nameSupplier)