input: Write a function to get the third largest element in a given row. If the list has fewer than three distinct elements, return None. Otherwise, return the third largest element. Function should have one parameter which is a list of integers.
  assert third_largest([12, 13, 13, 45, 22, 99])==22
  assert third_largest([1, 2, 3])==1
  assert third_largest([1, 2])==None
  assert third_largest([100, 50, 75, 75, 90])==75
  assert third_largest([1, 1, 1])==None
output: def third_largest(lst):
      distinct_elements = sorted(set(lst), reverse=True)
      if len(distinct_elements) < 3:
          return None
      return distinct_elements[2]