public sealed class KnowledgeGraphLayer : CompositeLayerWithTables, ArcGIS.Desktop.Core.IMetadataInfo, ILayerContainer, IMetadataSource, IStandaloneTableContainer, System.ComponentModel.INotifyPropertyChanged  

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
    }
  }
});

QueuedTask.Run(() =>
{
  //With a connection to a KG established or source uri available...
  //Create a KnowledgeGraphLayerCreationParams
  var kg_params = new KnowledgeGraphLayerCreationParams(kg)
  {
    Name = "KG_With_All_Types",
    IsVisible = false
  };
  //Or
  var kg_params2 = new KnowledgeGraphLayerCreationParams(new Uri(url))
  {
    Name = "KG_With_All_Types",
    IsVisible = false
  };
  //Call layer factory with map or group layer container. 
  //A KG layer containing a feature layer and/or standalone table per
  //entity and relate type (except provenance) is created
  var kg_layer = LayerFactory.Instance.CreateLayer<KnowledgeGraphLayer>(
      kg_params, map);

});

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

if (map.MapType == MapType.LinkChart)
{
  // if map is of MapType.LinkChart then the first level
  // children of the kgLayer are of type LinkChartFeatureLayer
  var childLayers = kgLayer.Layers;
  foreach (var childLayer in childLayers)
  {
    if (childLayer is LinkChartFeatureLayer lcFeatureLayer)
    {
      var isEntity = lcFeatureLayer.IsEntity;
      var isRel = lcFeatureLayer.IsRelationship;

      // TODO - continue processing
    }
  }
}
else if (map.MapType == MapType.Map)
{
  // if map is of MapType.Map then the children of the
  // kgLayer are the standard Featurelayer and StandAloneTable
  var chidlren = kgLayer.GetMapMembersAsFlattenedList();
  foreach (var child in chidlren)
  {
    if (child is FeatureLayer fl)
    {
      // TODO - process the feature layer
    }
    else if (child is StandaloneTable st)
    {
      // TODO - process the standalone table
    }
  }
}