Cheng Yanqi, born in June 2000, is the youngest female bullet train mechanic in Yunnan Province. Under the influence of her father, she became a bullet train "doctor," checking the operation status of the bullet train's bottom and side components, down to the state of every screw and wire. At Kunming Bullet Train Institute, there are 200 bullet train mechanics like Cheng, who work hard to ensure the safe operation of bullet trains and the safe travel of passengers.