Supporters of the presidential candidate Muhammadu Buhari and his All Progressive Congress hits with a motorbike another supporter during celebrations in Kano March 31, 2015. Nigeria's opposition APC declared an election victory on Tuesday for former military ruler Buhari and said Africa's most populous nation was witnessing history with its first democratic transfer of power. (Photo by Goran Tomasevic/Reuters)

On the second straight day of record-setting temperatures, Maddy Hacker is hoisted up by friend Jasmine Harper, both of McLean, Virgnia, as they attempt an acrobatic stunt in front of the U.S. Capitol in Washington, U.S., February 21, 2018. (Photo by Kevin Lamarque/Reuters)

Members of the SubCielo company perform during the fifth annual Puerto Rico Circo Fest in San Juan, Puerto Rico, Saturday, March 10, 2018. The festival is held simultaneously in several spots on the streets of the Old San Juan city on March 10–11. (Photo by Ricardo Arduengo/AFP Photo)

Kayaks, 7, poses for a picture holding toy gun in a camp where Christians displaced by Islamic State militants are living, in Irbil, Iraq, Friday, December 23, 2016. Iraq’s Christians are marking the holiday in his camp for displaced people with a sense of worry and despair, unable to return to their towns they were forced to flee two years ago by the Islamic State group’s onslaught. (Photo by Manu Brabo/AP Photo)

CHINA: Customers eat at a restaurant as a cooked pig sits on a cart on the street outside in Hong Kong, China, December 12, 2016. (Photo by David Gray/Reuters)

A human rainbow is created at a BASEOrlando coordinated event, “Orlando Strong Body Paint”, on Friday, June 17, 2016 in Orlando, Fl. The group created the rainbow, composed of volunteers numbering the same as that of the victims of the Pulse shooting, as a visual reminder of the amount of lives lost. (Photos by Amanda Voisard/The Washington Post)

A group of people are seen on a Victoria line train in London, England during the first night of the Night Tube service on August 19 2016. The Central line and Victoria line are the first to operate a Night service with further lines expected to be running by the end of the year. (Photo by SWNS.com)

A visitor jumps for a photograph on the world's highest and longest glass-bottomed bridge above a valley in Zhangjiajie in China's Hunan Province on August 21, 2016. The bridge, which opened to the public on a trial basis on Saturday, spans 430 meters (1,410 feet) and rises about 300 meters (984 feet) above a valley in a scenic zone, making it the world's highest and longest glass-bottomed bridge according to Chinese state media. (Photo by Fred Dufour/AFP Photo)