In this photo taken on Thursday, July 23, 2015 migrants enter a train to Serbia at the railway station in the southern Macedonian town of Gevgelija. The country has become a major transit route for thousands of Middle Eastern and African refugees and migrants who cross over from Greece and then continue into Serbia. (Photo by Boris Grdanoski/AP Photo)

Nepalese police officers worship a dog during the dog festival as part of Tihar celebrations, also called Diwali, at the Central Police Dog Training School in Kathmandu, Nepal October 29, 2016. Dogs are worshipped to acknowledge their role in providing security during Tihar festival, one of the most important Hindu festivals that is also dedicated to the worship of the goddess of wealth Laxmi. (Photo by Navesh Chitrakar/Reuters)

Muay Thai boxer Nong Rose Baan Charoensuk, who is transgender, trains at a gym in Buriram province, Thailand, July 3, 2017. Born Somros Polchareon, Rose said she identified as a woman at an early age and began wearing makeup and a sports bra in the ring.(Photo by Athit Perawongmetha/Reuters)

People try to board an overcrowded passenger train as they travel home to celebrate Eid al-Fitr festival, which marks the end of the Muslim holy fasting month of Ramadan, at a railway station in Dhaka, Bangladesh, July 5, 2016. (Photo by Adnan Abidi/Reuters)

An exile Tibetan monk gestures as he makes a point in a dialectics debate with another monk, sitting right, at the Kirti monastery in Dharmsala, India, Monday, January 18, 2016. The debate is an essential part of their training as Buddhist monks. (Photo by Ashwini Bhatia/AP Photo)

An old locomotive train that was used for transporting coal is preserved as a monument at Ny-Alesund, in Svalbard, Norway, October 11, 2015. A Norwegian chain of islands just 1,200 km (750 miles) from the North Pole is trying to promote new technologies, tourism and scientific research in a shift from high-polluting coal mining that has been a backbone of the remote economy for decades. (Photo by Anna Filipova/Reuters)

New York City policemen tangled with demonstrators at a subway station on the opening day of the New York World's Fair, April 22, 1964. Youths attempted to stall the train, which was headed from the city to the fairgrounds, as a form of protest on behalf of civil rights for blacks. (Photo by Charles Gorry/AP Photo)

A US Army M1A2 SEP tank participates in the Strong Europe Tank Challenge 2017 at the military training area in Grafenwoehr, Germany, 12 May 2017. Six North Atlantic Treaty Organization (NATO) nations and partner nations, Austria, France, Germany, Poland, Ukraine and the USA are taking part in this competing exercise. (Photo by Christian Bruna/EPA)