public sealed class KnowledgeGraphLayerIDSet 

// get the active investigation view 
var iv = KnowledgeGraphInvestigationView.Active;
var serviceUri = iv.Investigation.ServiceUri;

// build a dictionary of records
var dict = new Dictionary<string, List<long>>();
//Each entry consists of the type name and corresponding lists of ids
dict.Add(first_entity, new List<long>() { 1, 5, 18, 36, 78 });

//Create the id set...
var idSet = KnowledgeGraphLayerIDSet.FromDictionary(new Uri(serviceUri), dict);

// select the records on the investigation view
iv.SetSelectedRecords(idSet, SelectionCombinationMethod.New);

// get the active investigation view
var iv = KnowledgeGraphInvestigationView.Active;

QueuedTask.Run(() =>
{
  // get the investigation
  var inv = iv.Investigation;

  // get the set of selected records
  var idSet = iv.GetSelectedRecords();

  // view these records in a link chart
  var map = MapFactory.Instance.CreateLinkChart("myLinkChart", new Uri(inv.ServiceUri), idSet);
  ProApp.Panes.CreateMapPaneAsync(map);
});

QueuedTask.Run(() =>
{
  // get the selection set
  var sSet = map.GetSelection();

  // translate to an KnowledgeGraphLayerIDSet
  //  if the selectionset does not contain any KG entity or relationship records
  //    then idSet will be null  
  var idSet = KnowledgeGraphLayerIDSet.FromSelectionSet(sSet);
  if (idSet == null)
    return;


  // you can use the idSet to create a new linkChart
  //   (using MapFactory.Instance.CreateLinkChart)
});