Hotel staff practice self-defence skills after a training session given by team member of Special Weapons and Tactics (SWAT) team, in Hangzhou, Zhejiang province, April 7, 2016. (Photo by Reuters/Stringer)

In this Sunday June 13, 1988 file photo West German police officers arrest an English soccer hooligan who sticks out his tongue. Rioting broke out between some 100 hooligans and the police in downtown Stuttgart, West Germany following the European Soccer Championships match between England and Ireland. England was defeated by Ireland 0-1. (Photo by Kraufmann/AP Photo/File)

Walkers cross the river Waalbrug during the first day of the 98th annual four-days walking event, the “Vierdaagse” in Nijmegen, Netherlands, July 15, 2014. The “Nijmeegse Vierdaagse” is an annual public four-day field march which is held since 1909 in the third week of July. (Photo by Erik van 't Wout/EPA)

A rebel fighter celebrates as his comrades fire a rocket barrage toward the positions of troops loyal to Libyan ruler Muammar Gaddafi April 14, 2011 west of Ajdabiyah, Libya. Rebels exchanged artillery and rocket fire with loyalist troops west of Ajdabiyah April 14 as the confict engulfing Libya continued. (Photo by Chris Hondros/Getty Images)

A protester jumps on the table in front of the European Central Bank President Mario Draghi during a news conference in Frankfurt, Germany April 15, 2015. (Photo by Kai Pfaffenbach/Reuters)

Camel racing made its debut in Paxford, Gloucestershire, England yesterday at a point-to-point event on April 22, 2019. Each of the four camels was sponsored by a local pub. (Photo by Paul Nicholls/The Times)

A bakery worker rides a bicycle as he carries fresh bread on his head in Cairo, Egypt, February 9, 2016. (Photo by Asmaa Waguih/Reuters)

Olaf Niess catches swans on the river Alster near the town hall in Hamburg, Germany, 17 November 2015. The Alster swans are moving to their ice-free winter quarters on the Eppendorf Muehlenteich millpond until spring. (Photo by Bodo Marks/EPA)