A woman waits at a polio immunisation health centre, in Maiduguri, Borno State, Nigeria, August 29, 2016. Nigeria's military has liberated large swathes of land from Boko Haram but a ride with an army convoy, all guns firing for fear of ambush, shows how far the northeast is from normality after a brutal Islamist insurgency that has displaced millions. (Photo by Afolabi Sotunde/Reuters)

Extras in the arena of the “Fete des Vignerons” (winegrowers' festival in French), during the last rehearsal in Vevey, Switzerland, 17 July 2019. Organized by the brotherhood of winegrowers, the event will celebrate winemaking from 18 July to 11 August. The arena has a capacity of 20,000 spectators and hosts a giant central LED floor of approximately 800 square meters. (Photo by Laurent Gilliéron/EPA/EFE)

Shaolin boys practice kung fu in the sweltering heat during the zen shaolin music ceremony at shaolin temple, Dengfeng, Henan province, China on August 4, 2019. Shaolin unique skills include: shaolin arhat formation, three gun sashimi, shaolin stick, shaolin stone lock skill, iron hand splitting bricks, water training, fist and foot sparring. (Photo by Sipa Asia/Rex Features/Shutterstock)

A woman sells chips in Abidjan, Ivory Coast on August 09, 2019. World's number one cacao producer Ivory Coast's capital Abidjan set peace after the 201011 Ivorian crisis. Women in Abidjan work in various jobs to help their families' budget. (Photo by Mahmut Serdar Alakus/Anadolu Agency via Getty Images)

A family feeds sheep on a farm for tourists in Nakhon Ratchasima province, Thailand on September 14, 2019. (Photo by Soe Zeya Tun/Reuters)

Katie Rose Hobbs and Kirsten Elizabeth Pobjoy of British Aerosuperbatics Wingwalking Team perform ballet in the air during Huangguoshu Waterfalls Flight Conference on August 3, 2018 in Anshun, Guizhou Province of China. Huangguoshu Waterfalls Flight Conference including 18 aircraft from seven aerobatic teams from all over the world kicked off on Friday. (Photo by VCG via Getty Images)

Servicewomen march during a rehearsal for the Independence Day military parade in central Kiev, Ukraine on August 20, 2018. (Photo by Gleb Garanich/Reuters)

A mannequin stands in a textile factory in Madrid, Spain May 19, 2014. (Photo by Andrea Comas/Reuters)