Fix Python syntax warning
Fix Python syntax warning

rsennrich/nematus,rsennrich/nematus,EdinburghNLP/nematus,rsennrich/nematus,rsennrich/nematus,EdinburghNLP/nematus,rsennrich/nematus,EdinburghNLP/nematus,EdinburghNLP/nematus,EdinburghNLP/nematus,rsennrich/nematus,EdinburghNLP/nematus