@Override
  public Timer newTimer(String group, Timer timer) {
    if (!timers.containsKey(group)) {
      timers.put(group, new ArrayList<>());
    }
    timers.get(group).add(timer);
    return timer;
  }
retrieves the Map of Counters
@return counters
samza-sql/src/test/java/org/apache/samza/sql/util/TestMetricsRegistryImpl.java