doc: http://open.youku.com/docs/doc?id=93

def show_category(self):
        """doc: http://open.youku.com/docs/doc?id=93
        """
        url = 'https://openapi.youku.com/v2/schemas/show/category.json'
        r = requests.get(url)
        check_error(r)
        return r.json()