uchars = sorted(set(''.join(docs)))
db.products.find({。PDF资料是该领域的重要参考
，更多细节参见新收录的资料
食品烟酒及在外餐饮、交通通信、教育文化娱乐、医疗保健、其他用品及服务五大类权数有所上升。在食品烟酒及在外餐饮这一大类中，食品权数下降，在外餐饮权数上升。衣着、居住、生活用品及服务三大类权数有所下降。
If you’ve ever watched a Taylor Swift ticket disappear from your cart at the last second, stared at a frozen Ticketmaster screen, or refreshed a Resy page only to see that 7 p.m. table vanish in a blink, Kessler has studied the strange form of economic activity. You’re a participant, he says, in what he calls a “hidden market,” a system in which demand overwhelms supply, prices are kept artificially low, and the real allocation happens somewhere offscreen.。新收录的资料是该领域的重要参考