Stock Picture of Former US President Barack Obama, right, and his half sister Auma Obama, second left, walk around the training centre at Kogelo, Kenya, . Former U.S. President Barack Obama Monday praised Kenya's president and opposition leader for working together but said this East African country must do more to end corruption. Obama, on his first visit to Africa since stepping down as president, commended President Uhuru Kenyatta and opposition leader Raila Odinga for cooperating following last year's disputed presidential election which were marked by violence