input: Write a function to get the third largest element in a given row. If the given row has fewer than 3 unique elements, return `None`.
  assert third_largest([12, 13, 13, 45, 22, 99])==22
  assert third_largest([5, 5, 5])==None
  assert third_largest([1, 2])==None
  assert third_largest([8, 8, 7, 7, 6, 6, 5, 5])==6
  assert third_largest([])==None
output: def third_largest(row):
      unique_elements = list(set(row))
      if len(unique_elements) < 3:
          return None
      unique_elements.sort(reverse=True)
      return unique_elements[2]