old_contents: """Return ordered groups of lessons."""
  
  from collections import OrderedDict
  
  
  def group_lessons_by_age(lessons):
      """Return ordered groups of lessons.
  
      Lessons are grouped by the lesson minimum age and maximum ages,
      and then order by number.
  
      Returns:
          A ordered dictionary of grouped lessons.
          The key is a tuple of the minimum age and maximum ages for
          the lessons.
          The value for a key is a sorted list of lessons.
          The dictionary is ordered by minimum age, then maximum age.
      """
      grouped_lessons = OrderedDict()
      lessons = lessons.order_by("min_age", "max_age", "number")
      for lesson in lessons:
          if (lesson.min_age, lesson.max_age) in grouped_lessons:
              grouped_lessons[(lesson.min_age, lesson.max_age)].append(lesson)
          else:
              grouped_lessons[(lesson.min_age, lesson.max_age)] = [lesson]
      return grouped_lessons
  
new_contents: """Return ordered groups of lessons."""
  
  from collections import OrderedDict
  
  
  def group_lessons_by_age(lessons):
      """Return ordered groups of lessons.
  
      Lessons are grouped by the lesson minimum age and maximum ages,
      and then order by number.
  
      Args:
          lessons: QuerySet of Lesson objects (QuerySet).
  
      Returns:
          A ordered dictionary of grouped lessons.
          The key is a tuple of the minimum age and maximum ages for
          the lessons.
          The value for a key is a sorted list of lessons.
          The dictionary is ordered by minimum age, then maximum age.
      """
      grouped_lessons = OrderedDict()
      lessons = lessons.order_by("min_age", "max_age", "number")
      for lesson in lessons:
          if (lesson.min_age, lesson.max_age) in grouped_lessons:
              grouped_lessons[(lesson.min_age, lesson.max_age)].append(lesson)
          else:
              grouped_lessons[(lesson.min_age, lesson.max_age)] = [lesson]
      return grouped_lessons
  
subject: Add missing args docstring details