src/vs/workbench/browser/parts/editor/editorsObserver.ts/EditorsObserver/toIdentifier
class EditorsObserver:	private toIdentifier(arg1: string | IResourceEditorInputIdentifier, editorId?: string | undefined): string {
		if (typeof arg1 !== 'string') {
			return this.toIdentifier(arg1.typeId, arg1.editorId);
		}

		if (editorId) {
			return `${arg1}/${editorId}`;
		}

		return arg1;
	}