input: Write a function to optimize a Python algorithm to find the greatest 2 numbers from a list of 10000 integers. The function should return a tuple with the greatest and the second greatest numbers. If the list has less than 2 elements, return None.
  assert get_greatest_2([1, 5, 3, 7, 4, 7, 8, 9, 2, 10, 6, 8])==(10, 9)
  assert get_greatest_2([3, 5, 4, 1, 2])==(5, 4)
  assert get_greatest_2([5, 5, 5, 5])==(5, 5)
  assert get_greatest_2([1])==None
  assert get_greatest_2([])==None
output: def get_greatest_2(lst):
      if len(lst) < 2:
          return None
      max1, max2 = float('-inf'), float('-inf')
      for num in lst:
          if num > max1:
              max2 = max1
              max1 = num
          elif num > max2:
              max2 = num
      return (max1, max2)