List enrolled courses.

        @return: List of enrolled courses.
        @rtype: [str]

def list_courses(self):
        """
        List enrolled courses.

        @return: List of enrolled courses.
        @rtype: [str]
        """
        course = CourseraOnDemand(session=self._session,
                                  course_id=None,
                                  course_name=None)
        return course.list_courses()