Wuhan might have said goodbye to the last medical assistance team to leave the city one week ago, but it won't forget the medics, who helped it, any time soon. A team of photographers from all over China took more than 42,000 portraits of the medical professionals working there, and some of the images debuted in a documentary titled "Witness." CGTN's Xu Mengqi talks to the lead photographer about those pictures and the stories behind.