docs: public void addDisconnectedEventListener(Executor executor, PeerDisconnectedEventListener listener) {
          peerDisconnectedEventListeners.add(new ListenerRegistration<>(checkNotNull(listener), executor));
          for (Peer peer : getConnectedPeers())
              peer.addDisconnectedEventListener(executor, listener);
          for (Peer peer : getPendingPeers())
              peer.addDisconnectedEventListener(executor, listener);
      }