A spectator cools herself at a water spraying fan at the Australian Open tennis championships in Melbourne, Australia, Tuesday, January 17, 2017. (Photo by Kin Cheung/AP Photo)

Tour guides wearing traditional Chinese dress practice smiling by biting chopsticks at Qingming Grand-River Park in Kaifeng, central China's Henan Province on March 2, 2017, aiming to provide better service for visitors. (Photo by IPA Asia via ZUMA Wire)

Participants in the Grelka Fest at the Sheregesh resort in Tashtagolsky District of Kemerovo Oblast, Russia on April 22, 2017. Russian girls marked the end of the ski season with a record-breaking bikini ski festival at Siberia’s top winter resort, Sheregesh. Some 1,498 skiers and snowboarders undressed to impress in the annual event as they took to the pistes under blues skies and sunshine in a bracing temperature of just 5°C. (Photo by Grelka Fest/The Siberian Times)

Students training to be flight attendants hold books on their heads, chopsticks in their mouths, and papers in between their knees, as they take part in a standing posture practice at a vocational school in Shijiazhuang, Hebei province, China May 4, 2017. (Photo by Reuters/Stringer)

The student Patricia Vasconcellos de Almeida, 22, tried to kiss one of the military police who formed a cordon ostensibly in front of the building Fetranspor (Federation of Transport Companies), in Rio de Janeiro, on June 27, 2013. (Photo by Zulmair Rocha/UOL)

Yannis Behrakis, one of Reuters' most decorated and best-loved photographers, has passed away after a long battle with cancer. He was 58. Here: A pro-government Sierra Leonean fighter bites a bullet as he takes position in no man's land 2 km ahead of Rogberi junction where evidence of executed UN troops were found after heavy fighting between government troops and RUF rebels 100 km north east of Freetown, Sierra Leone, May 23, 2000. (Photo by Yannis Behrakis/Reuters)

An artist's impression of a growing supermassive black hole located in the early Universe is seen in this NASA handout illustration released on June 15, 2011. Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-Ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies. (Photo by Reuters/NASA/Chandra X-Ray Observatory/A.Hobart)

Donald Ganslmeier, operator of the Motodrom, rides a motorbike inside the Motodrom during a press tour at Theresienwiese on the premises of the 182nd annual Oktoberfest in Munich, Germany, September 17, 2015. (Photo by Matthias Balk/EPA)