code: public static Deferred<Annotation> getAnnotation(final TSDB tsdb, 
        final long start_time) {
      return getAnnotation(tsdb, (byte[])null, start_time);
    }
docs: Attempts to fetch a global annotation from storage
  @param tsdb The TSDB to use for storage access
  @param start_time The start time as a Unix epoch timestamp
  @return A valid annotation object if found, null if not