public sealed class KnowledgeGraph : ArcGIS.Core.Data.Datastore, System.IDisposable  

string url = 
  @"https://acme.server.com/server/rest/services/Hosted/AcmeKnowledgeGraph/KnowledgeGraphServer";

QueuedTask.Run(() =>
{
  //Create a connection properties
  var kg_props =
      new KnowledgeGraphConnectionProperties(new Uri(url));
  try
  {
    //Open a connection
    using (var kg = new KnowledgeGraph(kg_props))
    {
      //TODO...use the KnowledgeGraph
    }
  }
  catch (GeodatabaseNotFoundOrOpenedException ex)
  {
    System.Diagnostics.Debug.WriteLine(ex.ToString());
  }
});

var kgLayer = MapView.Active.Map.GetLayersAsFlattenedList()
        .OfType<KnowledgeGraphLayer>().FirstOrDefault();

      
QueuedTask.Run(() =>
{
  // use the layer directly
  var datastore = kgLayer.GetDatastore();

  // or you can use any of the sub items since
  //KnowledgeGraphLayer is a composite layer - get the first 
  // child feature layer or standalone table
  var featlayer = kgLayer?.GetLayersAsFlattenedList()?
                  .OfType<FeatureLayer>()?.FirstOrDefault();
  KnowledgeGraph kg = null;
  if (featlayer != null)
  {
    using (var fc = featlayer.GetFeatureClass())
      kg = fc.GetDatastore() as KnowledgeGraph;
    //TODO use KnowledgeGraph
  }
  else
  {
    //try standalone table
    var stbl = kgLayer?.GetStandaloneTablesAsFlattenedList()?
                    .FirstOrDefault();
    if (stbl != null)
    {
      using (var tbl = stbl.GetTable())
        kg = tbl.GetDatastore() as KnowledgeGraph;
      //TODO use KnowledgeGraph
    }
  }
});