How did Yang Xingcheng find Li Lianying's lifeline?

When Yuan Shikai asked Yang Shiqi how to find Li Lianying's lifeline, Yang Shiqi replied that he couldn't tell. In fact, Prince Qing Beizi fell in love with the actor Yang Cuixi when he came to Zhili, and then Yang Shiqi helped Beizi get Yang Cuixi. When Beizi returned to Beijing, Yang Shiqi asked Beizi to send a message to Eunuch De, saying that he had found Eunuch De's blue baggage, which meant that he wanted to send money to Eunuch De. The key to Li Lianying's treasure was only kept by Li Lianying himself, and sometimes he gave it to Eunuch De for him to clean. Li Lianying's treasure was stolen by Eunuch De at the instruction of Yang Shiqi. Li Lianying was so angry that she couldn't find her baby. When Li Lianying had nothing to do, Yang Shiqi came forward to hand over Li Lianying's baby to Li Lianying. From this, Li Lianying owed Yuan Shikai a huge favor. Yuan Shikai relied on this favor to befriend Li Lianying and let Li Lianying As his source of information in the palace, Li Lianying can tell him any troubles. In fact, all this is just a trick played by Yang Shiqi