if (lines.length 0) yield lines;
一、从无到有：Sun City医疗体系的进化之路Sun City 由Del Webb公司创办，定位是“活跃退休人士社区”。但它的医疗服务，并非一开始就配齐，而是跟着居民需求，一步步迭代升级，大致分为四个阶段。
，更多细节参见Line官方版本下载
* @param arr 待排序数组
In a company-wide email, Spencer stated that he would stay on until the summer in an advisory role before, “starting the next chapter of my life”. For her part, Bond issued a statement on her LinkedIn account: “I’ve decided this is the right time for me to take my next step, both personally and professionally.” It was all extremely good natured, but its doubtful these airy missives tell the full tale.