Fixed slicing in Python interface
Fixed slicing in Python interface


Former-commit-id: 98582c4244e7413bd387624d316cf971d216a777
danielhers/dynet,shuheik/dynet,chunyang-wen/dynet,clab/dynet,danielhers/dynet,danielhers/dynet,clab/cnn,danielhers/dynet,shuheik/dynet,shuheik/dynet,danielhers/dynet,chunyang-wen/dynet,clab/dynet,clab/dynet,clab/dynet,clab/dynet,xunzhang/dynet,danielhers/dynet,shuheik/dynet,shuheik/dynet,shuheik/dynet,clab/dynet,chunyang-wen/dynet,danielhers/dynet,clab/dynet,clab/cnn,xunzhang/dynet,chunyang-wen/dynet,xunzhang/dynet,xunzhang/dynet,shuheik/dynet,clab/cnn