public Dictionary<string,List<long>> ToOIDDictionary()

{
  var kg_layer = MapView.Active.Map.GetLayersAsFlattenedList()
                  .OfType<KnowledgeGraphLayer>().FirstOrDefault();
  if (kg_layer == null)
    return;

  await QueuedTask.Run(() =>
  {
    //Get the existing kg layer id set and convert to a dictionary
    var layer_id_set = kg_layer.GetIDSet();
    var dict = layer_id_set.ToOIDDictionary();//Empty list means all records

    //Create an id set from a dictionary
    var dict2 = new Dictionary<string, List<long>>();
    dict2.Add("Enity_Or_Relate_Type_Name1", null);//Null means all records
    dict2.Add("Enity_Or_Relate_Type_Name2", new List<long>());//Empty list means all records
    dict2.Add("Enity_Or_Relate_Type_Name3",
      new List<long>() { 3, 5, 9, 101, 34 });//Explicit list of ids
                                             //dict2.Add("Enity_Or_Relate_Type_Name4",
                                             // new List<long>() { etc, etc });

    //Create the id set
    var idset = KnowledgeGraphLayerIDSet.FromDictionary(kg, dict2);

    //Can be used to create a layer, link chart, append to link chart, etc...
  });
}

{
        await QueuedTask.Run(() =>
{
  var idSet = kgLayer.GetIDSet();

  // is the set empty?
  var isEmpty = idSet.IsEmpty;
  // get the count of named object types
  var countNamedObjects = idSet.NamedObjectTypeCount;
  // does it contain the entity "Species";
  var contains = idSet.Contains("Species");

  // get the idSet as a dictionary of namedObjectType and oids
  var oidDict = idSet.ToOIDDictionary();
  var speciesOIDs = oidDict["Species"];

  // alternatively get the idSet as a dictionary of 
  // namedObjectTypes and uuids
  var uuidDict = idSet.ToUIDDictionary();
  var speciesUuids = uuidDict["Species"];

});
      }