Fix error in example code in documentation.
Fix error in example code in documentation.

fabianrost84/cython,ChristopherHogan/cython,fabianrost84/cython,cython/cython,c-blake/cython,scoder/cython,da-woods/cython,c-blake/cython,c-blake/cython,da-woods/cython,c-blake/cython,scoder/cython,fabianrost84/cython,fabianrost84/cython,cython/cython,cython/cython,ChristopherHogan/cython,c-blake/cython,scoder/cython,cython/cython,scoder/cython,ChristopherHogan/cython,fabianrost84/cython,da-woods/cython,da-woods/cython