src/vs/editor/contrib/codelens/browser/codeLensCache.ts/CodeLensCache/_serialize
class CodeLensCache:	private _serialize(): string {
		const data: Record<string, ISerializedCacheData> = Object.create(null);
		for (const [key, value] of this._cache) {
			const lines = new Set<number>();
			for (const d of value.data.lenses) {
				lines.add(d.symbol.range.startLineNumber);
			}
			data[key] = {
				lineCount: value.lineCount,
				lines: [...lines.values()]
			};
		}
		return JSON.stringify(data);
	}