public Dictionary<int,string> GetAvailableClassCodesAndLabels()

{
  // Note: call within QueuedTask.Run()
  {
    Dictionary<int, string> classCodesAndLabels =
                    pointCloudSceneLayer.GetAvailableClassCodesAndLabels();
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    //Retrieve the available classification codes
    var dict = pointCloudSceneLayer.GetAvailableClassCodesAndLabels();

    //Filter out low noise and unclassified (7 and 1 respectively)
    //consult https://pro.arcgis.com/en/pro-app/help/data/las-dataset/storing-lidar-data.htm
    var filterDef = new PointCloudFilterDefinition()
    {
      ClassCodes = dict.Keys.Where(c => c != 7 && c != 1).ToList(),
      ReturnValues = new List<PointCloudReturnType> {
                        PointCloudReturnType.FirstOfMany }
    };
    //apply the filter
    pointCloudSceneLayer.SetFilters(filterDef.ToCIM());
  }
}