public static Mapper<List<List<Span>>, List<List<Span>>> filterTraces(Iterable<String> traceIds) {
    return new FilterTracesByIds(traceIds);
  }
Returns a function that filters its mutable input when it contains a trace not matching the
specified trace IDs.

<p>Make sure the input IDs are unique and {@link Span#normalizeTraceId(String) normalized}.
zipkin/src/main/java/zipkin2/storage/StrictTraceId.java