input: Write a function to find the third largest element in a given list. If the list has fewer than three elements, return None.
  def third_largest(lst):
      if len(lst) < 3:
          return None
      distinct = []
      for i in lst:
          if i not in distinct:
              distinct.append(i)
      distinct.sort(reverse=True)
      return distinct[2]
  
  assert third_largest([12, 13, 13, 45, 22, 99])==22
  assert third_largest([1, 2])==None
  assert third_largest([7, 7, 7, 7, 7])==7
  assert third_largest([34, 12, 45, 99, 45])==34
  assert third_largest([])==None
output: def third_largest(lst):
      if len(lst) < 3:
          return None
      distinct = []
      for i in lst:
          if i not in distinct:
              distinct.append(i)
      distinct.sort(reverse=True)
      return distinct[2]