A girl salutes to visitors before a show at the Mangyongdae Children's Palace in central Pyongyang, North Korea May 5, 2016. Pyongyang held a gala of song and dance performances by local school children on May 5 for visiting delegations of foreign journalists and tourists at the Mangyongdae Children's Palace. The event included orchestral, choir, and acrobatic performances, many of them with political undertones. The Seventh Worker's Party Congress commences on May 6, 2016. (Photo by Damir Sagolj/Reuters)

The US Navy Blue Angels numbers 5 and 6 fly below Sean Tucker (above) as he pilots the Oracle Challenger III over San Francisco, California as part of a practice run for Fleet Week on October 6, 2016. (Photo by Josh Edelson/AFP Photo)

A child plays the ice slide at the Ice-Snow World park in Harbin, capital of northeast China's Heilongjiang Province, January 5, 2017. The theme park which used about 330,000 cubic meters of ice and snow for construction opened on Thursday. (Photo by Xinhua/Barcroft Images)

A member of the Tinstix of Dynamite aerobatics team flies in front of a wall of fire during the Australian International Airshow in Melbourne on March 5, 2017. The annual event sees 180,000 visitors over the 3-day public event held at the Avalon Airfield some 80kms south-west of Melbourne. (Photo by Mal Fairclough/AFP Photo)

Iranian women perform as they train Far East Fighting Arts to be able to defend themselves, at the Jughin castle which is located 40 km's far from Tehran, Iran on June 5, 2017. (Photo by Fatemeh Bahrami/Anadolu Agency/Getty Images)

A woman rides the world's longest urban zip line, with a speed of up to 80 kilometers per hour on a one kilometer run from 170 meter to ground level, in the Marina district of Dubai, United Arab Emirates, Tuesday, December 5, 2017. (Photo by Kamran Jebreili/AP Photo)

A woman holds a hedgehog at the Harry hedgehog cafe in Tokyo, Japan, April 5, 2016. In a new animal-themed cafe, 20 to 30 hedgehogs of different breeds scrabble and snooze in glass tanks in Tokyo's Roppongi entertainment district. Customers have been queuing to play with the prickly mammals, which have long been sold in Japan as pets. The cafe's name Harry alludes to the Japanese word for hedgehog, harinezumi. (Photo by Thomas Peter/Reuters)

A Mexican wearing a period costume re-enacts the battle of Puebla, in the Penon de los Banos neighbourhood of Mexico City, Mexico May 5, 2016. The battle marked the defeat of French forces by Mexican troops and local Indians in the central state of Puebla in 1862. During the re-enactment, participants fired homemade shotguns loaded with gunpowder and hundreds of men dressed as Indian peasants fought mock battles against others dressed as French invaders. (Photo by Henry Romero/Reuters)