Rescue workers help the injured at the site of a multi-storey building collapse in the capital Nairobi, Kenya Sunday, January 4, 2015. The residential building in the Huruma neighborhood of Nairobi collapsed on Sunday and according to the Kenya Red Cross, a dozen people have so far been rescued but an unknown number are still feared trapped. (Photo by AP Photo)

SpaceX’s Dragon spacecraft, March 6, 2014. SpaceX's Falcon 9 rocket and Dragon spacecraft launched from Launch Complex 40 at the Cape Canaveral Air Force Station, Florida, for their third official Commercial Resupply (CRS) mission to the orbiting lab on April 18, 2014. Dragon returned to Earth with a parachute-assisted splashdown off the coast of southern California on May 14, 2014. Dragon is the only operational spacecraft capable of returning a significant amount of supplies back to Earth, including experiments. (Photo by Ron Lin/SpaceX Photos)

Afghanistan's interior ministry special forces demonstrate their skills during a military exercise in Kabul, Afghanistan, Thursday, April 2, 2015. Afghanistan's security forces took over full responsibility for the country's security on January 1, 2015. (Photo by Massoud Hossaini/AP Photo)

A worker walks beside the ocean liner Queen Mary II in a dock at Blohm&Voss shipyard in Hamburg, Germany, June 14, 2016. The mighty Queen Mary 2 is just days away from setting sail after the most expensive refurbishment of any ship in history. Tens of millions of pounds have been spent on the 151,200-tonne ship as 2,500 workers complete the month-long major interior overhaul. (Photo by Fabian Bimmer/Reuters)

A girl looks at other children practicing on a boxing ring during an exercise session at a boxing school, in the Mare favela of Rio de Janeiro, Brazil, June 2, 2016. For many young residents the Luta Pela Paz (Fight For Peace) academy offers a glimpse of an alternative: a chance to build discipline and self-esteem through boxing and martial arts. (Photo by Nacho Doce/Reuters)

Relatives clean the body of Paul Sampe Lumba who has been dead for seven yeas during the Ma'nene ritual at Panggala Village on August 26, 2016 in Toraja, Indonesia. The Ma'nene ritual in performed during a ceremony every three years, where the dead are exhumed for a change of clothes, among the people of Toraja as an expression of the love of the surviving family. (Photo by Sijori Images/Barcroft Images)

A member of the “Exit Point” amateur rope-jumping group jumps from a 44-metre high (144-feet high) waterpipe bridge in the Siberian Taiga area outside Krasnoyarsk, September 28, 2014. Fans of rope-jumping, a kind of extreme sport involving a jump from a high point using an advanced system of amortization including mountaineering and rope safety equipment, attended the Golden Autumn group's jumping season. (Photo by Ilya Naymushin/Reuters)

In this photograph taken on Thursday, November 20, 2014, bud tenders Maxwell Bradford, back left, and Emma Attolini display buds in the shape of Christmas trees that are on sale for the holiday season in a recreational marijuana shop in northwest Denver. The nascent marijuana industry in Colorado is targeting holiday shoppers with special deals much like traditional retailers offer. (Photo by David Zalubowski/AP Photo)