docs: def list_courses(self):
          """
          List enrolled courses.
  
          @return: List of enrolled courses.
          @rtype: [str]
          """
          reply = get_page(self._session, OPENCOURSE_MEMBERSHIPS, json=True)
          course_list = reply['linked']['courses.v1']
          slugs = [element['slug'] for element in course_list]
          return slugs