void handleIncompleteRpc(Span.Builder next) {
    if (Kind.CLIENT.equals(next.kind())) {
      if (cs != null) next.timestamp(cs.timestamp);
      if (cr != null) next.addAnnotation(cr.timestamp, cr.value);
    } else if (Kind.SERVER.equals(next.kind())) {
      if (sr != null) next.timestamp(sr.timestamp);
      if (ss != null) next.addAnnotation(ss.timestamp, ss.value);
    }
  }
Allows you to split a v1 span when necessary. This can be the case when reading merged
client+server spans from storage or parsing old data formats.

<p>This type isn't thread-safe: it re-uses state to avoid re-allocations in conversion loops.
zipkin/src/main/java/zipkin2/v1/V1SpanConverter.java