src/vs/workbench/api/browser/mainThreadCodeInsets.ts/MainThreadEditorInsets/getInset
class MainThreadEditorInsets:	private getInset(handle: number): EditorWebviewZone {
		const inset = this._insets.get(handle);
		if (!inset) {
			throw new Error('Unknown inset');
		}
		return inset;
	}