public void removeListener(EndpointManager.EndpointListener listener) {
      HashSet<EndpointListener> tmpListeners = new HashSet<>(endpointListeners);
      tmpListeners.remove(listener);
      endpointListeners = Collections.unmodifiableSet(tmpListeners);
    }
Used by Endpoint only, when the reference count for this endpoint reaches 0
geode-core/src/main/java/org/apache/geode/cache/client/internal/EndpointManagerImpl.java