add containsChild method to ThermionAsset

thermion_dart/lib/src/filament/src/implementation/ffi_asset.dart

@@ -9,6 +9,7 @@ import 'package:thermion_dart/thermion_dart.dart';
 import 'package:vector_math/vector_math_64.dart' as v64;
 
 class FFIAsset extends ThermionAsset {
+  
   T getHandle<T>() {
     return asset as T;
   }
@@ -934,4 +935,12 @@ class FFIAsset extends ThermionAsset {
   Future<int> getPrimitiveCount({ThermionEntity? entity}) async {
     return FilamentApp.instance!.getPrimitiveCount(entity ??= this.entity);
   }
+  
+  ///
+  ///
+  ///
+  @override
+  Future<bool> containsChild(ThermionEntity entity) async {
+    return (await getChildEntities()).contains(entity);
+  }
 }

thermion_dart/lib/src/filament/src/interface/asset.dart

@@ -21,7 +21,6 @@ export 'geometry.dart';
 ///
 ///
 abstract class ThermionAsset {
-
   ///
   ///
   ///
@@ -39,6 +38,13 @@ abstract class ThermionAsset {
   ///
   Future<List<ThermionEntity>> getChildEntities();
 
+  ///
+  ///
+  ///
+  Future<bool> containsChild(ThermionEntity entity) {
+    throw UnimplementedError();
+  }
+
   ///
   ///
   ///