private Set<InternalDistributedMember> sendViaMembershipManager(
      List<InternalDistributedMember> destinations,
      DistributionMessage content, ClusterDistributionManager dm, DistributionStats stats)
      throws NotSerializableException {
    if (distribution == null) {
      logger.warn("Attempting a send to a disconnected DistributionManager");
      if (destinations.size() == 1 && destinations.get(0) == Message.ALL_RECIPIENTS) {
        return null;
      }
      return new HashSet<>(destinations);
    }

    return distribution.send(destinations, content);
  }
@return list of recipients who did not receive the message because they left the view (null if
        all received it or it was sent to {@link Message#ALL_RECIPIENTS}).
@throws NotSerializableException If content cannot be serialized
geode-core/src/main/java/org/apache/geode/distributed/internal/ClusterDistributionManager.java