src/vs/platform/contextkey/browser/contextKeyService.ts/ScopedContextKeyService/createChildContext
class ScopedContextKeyService:	public createChildContext(parentContextId: number = this._myContextId): number {
		if (this._isDisposed) {
			throw new Error(`ScopedContextKeyService has been disposed`);
		}
		return this._parent.createChildContext(parentContextId);
	}