docs: @Override
      public ScheduledEntry<K, V> get(K key) {
          synchronized (mutex) {
              if (scheduleType.equals(ScheduleType.FOR_EACH)) {
                  return getByCompositeKey(key);
              }
              Integer second = secondsOfKeys.get(key);
              if (second != null) {
                  Map<Object, ScheduledEntry<K, V>> entries = scheduledEntries.get(second);
                  if (entries != null) {
                      return entries.get(key);
                  }
              }
              return null;
          }
      }