public string GetShapeField()

await QueuedTask.Run(() =>
{
  using (var kg = GetKnowledgeGraph())
  {
    if (kg == null)
      return;

    var entity_name = "PhoneCall";
    var relate_name = "WhoCalledWho";

    var kvp_entity = kg.GetDataModel().GetEntityTypes()
         .First(r => r.Key == entity_name);
    var kvp_relate = kg.GetDataModel().GetRelationshipTypes()
                   .First(r => r.Key == relate_name);

    //Let's delete one field and add a new one from each
    //A field gets deleted implicitly if it is not included in the list of
    //fields - or "properties" in this case....so we will remove the last
    //property from the list
    var entity_props = kvp_entity.Value.GetProperties().Reverse().Skip(1).Reverse();
    var prop_descs = new List<KnowledgeGraphPropertyDescription>();

    foreach (var prop in entity_props)
    {
      if (prop.FieldType == FieldType.Geometry)
      {
        continue;//skip shape
      }
      var prop_desc = new KnowledgeGraphPropertyDescription(prop);
      prop_descs.Add(prop_desc);
    }
    //deal with shape - we need to keep it
    //SchemaBuilder deletes any field not included in the "modify" list
    ShapeDescription shape_desc = null;
    if (kvp_entity.Value.GetIsSpatial())
    {
      var geom_def = kvp_entity.Value.GetShapeDefinition();
      var shape_name = kvp_entity.Value.GetShapeField();
      shape_desc = new ShapeDescription(
        shape_name, geom_def.geometryType, geom_def.sr);
    }
    //add the new entity property
    prop_descs.Add(
      KnowledgeGraphPropertyDescription.CreateStringProperty("foo", 10));
    //make a description for the entity type - ok if shape_desc is null
    var entityDesc = new KnowledgeGraphEntityTypeDescription(
      entity_name, prop_descs, shape_desc);

    //Add the entity type description to the schema builder using 'Modify'
    SchemaBuilder sb = new(kg);
    sb.Modify(entityDesc);

    //Repeat for the relationship - assuming we have at least one custom attribute field
    //that can be deleted on our relationship schema...
    var rel_props = kvp_relate.Value.GetProperties().Reverse().Skip(1).Reverse();
    var rel_prop_descs = new List<KnowledgeGraphPropertyDescription>();

    foreach (var prop in rel_props)
    {
      if (prop.FieldType == FieldType.Geometry)
      {
        continue;//skip shape
      }
      var prop_desc = new KnowledgeGraphPropertyDescription(prop);
      rel_prop_descs.Add(prop_desc);
    }
    //deal with shape - we need to keep it
    //SchemaBuilder deletes any field not included in the "modify" list
    ShapeDescription shape_desc_rel = null;
    if (kvp_relate.Value.GetIsSpatial())
    {
      var geom_def = kvp_relate.Value.GetShapeDefinition();
      var shape_name = kvp_relate.Value.GetShapeField();
      shape_desc_rel = new ShapeDescription(
        shape_name, geom_def.geometryType, geom_def.sr);
    }
    //add a new relationship property
    rel_prop_descs.Add(
      KnowledgeGraphPropertyDescription.CreateStringProperty("bar", 10));
    //make a description for the relationship type - ok if shape_desc is null
    var relDesc = new KnowledgeGraphRelationshipTypeDescription(
      relate_name, rel_prop_descs, shape_desc_rel);

    //Add the relationship type description to the schema builder using 'Modify'
    sb.Modify(relDesc);

    //Run the schema builder
    try
    {
      //Use the KnowledgeGraph extension method 'ApplySchemaEdits(...)'
      //to refresh the Pro UI
      if (!kg.ApplySchemaEdits(sb))
      {
        var err_msg = string.Join(",", sb.ErrorMessages.ToArray());
        System.Diagnostics.Debug.WriteLine($"Entity/Relate Modify error: {err_msg}");
      }
    }
    catch (Exception ex)
    {
      System.Diagnostics.Debug.WriteLine(ex.ToString());
    }
  }
});