docs: public BaseMessageFilter findMessageFilter(JMessageListener listener)
      {
          Iterator<BaseMessageFilter> iterator = m_mapFilters.values().iterator();
          while (iterator.hasNext())
          {
              BaseMessageFilter filter = iterator.next();
              for (int i = 0; (filter.getMessageListener(i) != null); i++)
              {
                  if (filter.getMessageListener(i) == listener)
                      return filter;
              }
          }
          return null;    // Error, not found.
      }