input: Write a function to get 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, 3, 4, 5])==3
  assert third_largest([10, 20])==None
  assert third_largest([30, 30, 20, 20, 10, 10])==20
  assert third_largest([1])==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]