docs: protected boolean seenByInterconnectedPeers( Set<Long> destinations, Set<Long> origins) {
          Set<Long> seers = Multimaps.filterValues(m_alive, in(origins)).keySet();
          int before = origins.size();
  
          origins.addAll(seers);
          if (origins.containsAll(destinations)) {
              return true;
          } else if (origins.size() == before) {
              return false;
          }
          return seenByInterconnectedPeers(destinations, origins);
      }