@Override Collection<Span> valueContainer() {
        return new LinkedHashSet<>();
      }
Primary source of data is this map, which includes spans ordered descending by timestamp. All
other maps are derived from the span values here. This uses a list for the spans, so that it is
visible (via /api/v2/trace/{traceId}) when instrumentation report the same spans multiple
times.
zipkin/src/main/java/zipkin2/storage/InMemoryStorage.java