observablePart as method pon deepState

src/Umbraco.Web.UI.Client/libs/observable-api/deep-state.ts

@@ -1,4 +1,5 @@
 import { BehaviorSubject } from "rxjs";
+import { createObservablePart } from "./create-observable-part.method";
 
 
 // TODO: Should this handle array as well?
@@ -50,6 +51,13 @@ export class DeepState<T> extends BehaviorSubject<T> {
 		super(deepFreeze(initialData));
 	}
 
+	observablePart<ReturnType>(
+		mappingFunction: MappingFunction<T, ReturnType>,
+		memoizationFunction?: MemoizationFunction<ReturnType>
+	) {
+		return createObservablePart(this, mappingFunction, memoizationFunction);
+	}
+
 	next(newData: T): void {
 		const frozenData = deepFreeze(newData);
 		// Only update data if its different than current data.