class SpanBuilderSdk implements Span.Builder {

  @Override
  public Span.Builder setStartTimestamp(long startTimestamp) {
    Utils.checkArgument(startTimestamp >= 0, "Negative startTimestamp");
    startEpochNanos = startTimestamp;
    return this;
  }

    SpanBuilderSdk(
      String spanName,
      InstrumentationLibraryInfo instrumentationLibraryInfo,
      SpanProcessor spanProcessor,
      TraceConfig traceConfig,
      Resource resource,
      IdsGenerator idsGenerator,
      Clock clock);

}