code: private void cleanup_heartbeat_filters() {
          Enumeration channel_names = channel_map.keys();
          while (channel_names.hasMoreElements()) {
              String name = (String) channel_names.nextElement();
              EventChannelStruct eventChannelStruct = channel_map.get(name);
              if (eventChannelStruct.consumer instanceof NotifdEventConsumer) {
                  try {
                      int filter_id = eventChannelStruct.heartbeat_filter_id;
                      Filter filter =
                              eventChannelStruct.structuredProxyPushSupplier.get_filter(filter_id);
                      eventChannelStruct.structuredProxyPushSupplier.remove_filter(filter_id);
                      filter.destroy();
                  } catch (FilterNotFound e) {
                      //  do nothing
                  }
              }
          }
      }
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