docs: public void addGetDataEventListener(final Executor executor, final GetDataEventListener listener) {
          peerGetDataEventListeners.add(new ListenerRegistration<>(checkNotNull(listener), executor));
          for (Peer peer : getConnectedPeers())
              peer.addGetDataEventListener(executor, listener);
          for (Peer peer : getPendingPeers())
              peer.addGetDataEventListener(executor, listener);
      }