input: 
  def third_largest(lst):
      """
      Given a list of numbers, return the third largest element. 
      If the list has fewer than 3 elements, return None.
      >>> third_largest([12, 13, 13, 45, 22, 99])
      22
      """
      if len(lst) < 3:
          return None
      distinct = sorted(set(lst), reverse=True)
      if len(distinct) < 3:
          return None
      return distinct[2]
  
output:     if len(lst) < 3:
          return None
      distinct = sorted(set(lst), reverse=True)
      if len(distinct) < 3:
          return None
      return distinct[2]