code: def skip(course, num=1):
      
      sel = None
      try:
          sel = Exercise.get_selected()
          if sel.course.tid != course.tid:
              sel = None
      except NoExerciseSelected:
          pass
  
      if sel is None:
          sel = course.exercises.first()
      else:
          try:
              sel = Exercise.get(Exercise.id == sel.id + num)
          except peewee.DoesNotExist:
              print("There are no more exercises in this course.")
              return False
  
      sel.set_select()
      list_all(single=sel)
docs: Go to the next exercise.