Why does Wuxi's personal doorbell code remind you of tin withdrawal?

In Wuxi, the reason why the personal doorbell code prompts tin to tin is to prompt nucleic acid. According to the relevant public information, in order to improve the scientific and accurate prevention and control ability and improve the sensitivity of monitoring and early warning, all people who come to (return to) Tin will receive a pop-up prompt when they show their personal doorbell code or scan the doorbell code with Linxi App after arriving in Tin, reminding them to implement their obligations related to epidemic prevention and control such as nucleic acid detection and health monitoring.