code: public Span nextSpan(Message<?> message) {
  		MessageHeaderAccessor headers = mutableHeaderAccessor(message);
  		TraceContextOrSamplingFlags extracted = this.extractor.extract(headers);
  		headers.setImmutable();
  		Span result = this.tracer.nextSpan(extracted);
  		if (extracted.context() == null && !result.isNoop()) {
  			addTags(message, result, null);
  		}
  		if (log.isDebugEnabled()) {
  			log.debug("Created a new span " + result);
  		}
  		return result;
  	}
docs: Use this to create a span for processing the given message. Note: the result has no
  name and is not started.
  <p>
  <p>
  This creates a child from identifiers extracted from the message headers, or a new
  span if one couldn't be extracted.
  @param message message to use for span creation
  @return span to be created