code: @Override
      public Calendar retrieveCalendar(final String calName) throws JobPersistenceException {
          return doWithLock(new LockCallback<Calendar>() {
              @Override
              public Calendar doWithLock(JedisCommands jedis) throws JobPersistenceException {
                  return storage.retrieveCalendar(calName, jedis);
              }
          }, "Could not retrieve calendar.");
      }
docs: Retrieve the given <code>{@link org.quartz.Trigger}</code>.
  
  @param calName The name of the <code>Calendar</code> to be retrieved.
  @return The desired <code>Calendar</code>, or null if there is no
  match.