WatchlistRemovedEventArgs

 using cAlgo.API;
 namespace cAlgo
 {
     // This sample shows how to use WatchlistRemovedEventArgs
     [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
     public class WatchlistRemovedEventArgsSample : Indicator
     {
         protected override void Initialize()
         {
             Watchlists.Removed += OnWatchlistsRemoved;
         }
         private void OnWatchlistsRemoved(WatchlistRemovedEventArgs obj)
         {
             Print("Watchlist {0} removed", obj.Watchlist.Name);
         }
         public override void Calculate(int index)
         {
         }
     }
 }

 import clr
 clr.AddReference("cAlgo.API")
 from cAlgo.API import *
 class Test():    
     def initialize(self):
         api.Watchlists.Removed += self.on_watchlists_removed
     def on_watchlists_removed(self, args):
         print(f"Watchlist {args.Watchlist.Name} removed")