docs: public int numBroadcastPeers(Sha256Hash txHash) {
          lock.lock();
          try {
              cleanTable();
              WeakConfidenceReference entry = table.get(txHash);
              if (entry == null) {
                  return 0;  // No such TX known.
              } else {
                  TransactionConfidence confidence = entry.get();
                  if (confidence == null) {
                      // Such a TX hash was seen, but nothing seemed to care so we ended up throwing away the data.
                      table.remove(txHash);
                      return 0;
                  } else {
                      return confidence.numBroadcastPeers();
                  }
              }
          } finally {
              lock.unlock();
          }
      }