Robot couple Xiaolan (L) and Xiaotao carry trays of food at a restaurant in Jinhua, Zhejiang province, China, May 18, 2015. The restaurant, which opened on Monday, has two robots delivering food for customers. The robots were designed as a couple, Xiaolan and Xiaotao, according to local media. (Photo by Reuters/Stringer)

Riot police stand guard behind a fire as refinery workers hold a blockade of the oil depot of Douchy-Les-Mines to protest against the government's proposed labour reforms, on May 25, 2016. Refinery workers stepped up strikes that threaten to paralyse France weeks ahead of the Euro 2016 tournament as the government moved to break their blockades, escalating a three-month tug-of-war over labour reforms. (Photo by François L.O./AFP Photo)

Aerobatic pilot Sean D. Tucker flies in the two-seat Oracle Extra airplane over downtown Chicago skyline, Wednesday, June 8, 2016. Tucker will perform before the start of of the America's Cup World Series racing on Saturday and Sunday. (Photo by Kiichiro Sato/AP Photo)

Freshmen in Zhengzhou Institute of Aeronautical Industry Management head bottles of mineral water for upright stand during military training on September 17, 2015 in Zhengzhou, Henan Province of China. More than 6,800 freshmen in the school are required to take part in the military training. (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

US model Binx Walton strutted out with a boob exposed and only a glittery love heart ­protecting her modesty in Anthony Vaccarello’s debut show for Saint ­Laurent on September 27, 2016. The Sun found out how the trend measured up on trip to the shops. Here: Isabella Besque 21 from London tries out the nipple cover look as seen Paris Fashion week on the streets of London, England on October 7, 2016. (Photo by Stewart Williams/The Sun)

A child walks to an installation made from fallen leaves by college students, in shape of a sofa, to call for people's attention to environment protection, in Hangzhou, Zhejiang province, China, December 6, 2016. (Photo by Reuters/China Daily)

ESA astronaut Samantha Cristoforetti on the International Space Station 3 February 2015 during her Futura mission. Samantha is living and working on the Station as part of the Expedition 42 crew. Picture released on February 10, 2015. (Photo by ESA/NASA)

David Pena poses for a photograph with his Lada 2101 built in 1979 on a street in Havana February 9, 2015. Getting parts from the United States is cheaper than in Cuba, where state-run stores sell them at four times the cost, said Pena, a mechanic and president of the Russian Car Club in Havana who drives a souped-up, sporty red 1972 Lada 2101 that he fixed himself. His own Lada has a Fiat engine and an extra Alfa Romeo carburetor. (Photo by Enrique De La Osa/Reuters)