ChartObjectsEventArgs

 using cAlgo.API;
 namespace cAlgo
 {
     // This example shows how to use the Chart ChartObjectsEventArgs
     // All chart objects related events args are derived from ChartObjectsEventArgs
     [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
     public class ChartObjectsEventArgsSample : Indicator
     {
         protected override void Initialize()
         {
             Chart.ObjectsRemoved += Chart_ObjectsRemoved;
         }
         private void Chart_ObjectsRemoved(ChartObjectsRemovedEventArgs obj)
         {
             var chartObjectsEventArgs = obj as ChartObjectsEventArgs;
             Print("{0} objects removed from chart", chartObjectsEventArgs.ChartObjects.Count);
         }
         public override void Calculate(int index)
         {
         }
     }
 }

 import clr
 clr.AddReference("cAlgo.API")
 from cAlgo.API import *
 class Test():    
     def initialize(self):
         api.Chart.ObjectsRemoved += self.on_chart_objects_removed
     def on_chart_objects_removed(self, args):
         print(f"{args.ChartObjects.Count} objects removed from chart")