if (len === 0) return [];
自上台以來，習近平發起多輪反腐運動，批評者認為，這些行動同時也被用來清除政治對手。
，更多细节参见夫子
Transforms don't execute until the consumer pulls. There's no eager evaluation, no hidden buffering. Data flows on-demand from source, through transforms, to the consumer. If you stop iterating, processing stops.
for (const auto &seg : segments) {