public Iterable<NodeSource> getNodeSources(ReferenceID nodeId) {
    if (myDelta != null) {
      Iterable<NodeSource> _src = myDelta.getSources(nodeId);
      Iterable<NodeSource> deltaSources = _src instanceof Set? _src : collect(_src, new HashSet<>()) /*ensure Set data structure*/;
      Set<NodeSource> deleted = myDelta.getDeletedSources();
      return flat(deltaSources, filter(myGraph.getSources(nodeId), src -> !contains(deltaSources, src) && !deleted.contains(src) && mySourcesFilter.test(src)));
    }
    return filter(myGraph.getSources(nodeId), mySourcesFilter::test);
  }
public Iterable<NodeSource> getNodeSources(ReferenceID nodeId)