input: Write a function to find and return the greatest 2 numbers from a list of integers. If the list is empty or contains less than 2 numbers, return None. 
  
  def get_greatest_2(items):
      if len(items) < 2:
          return None
      max1, max2 = float('-inf'), float('-inf')
      for item in items:
          if item > max1:
              max1, max2 = item, max1
          elif item > max2:
              max2 = item
      return max1, max2
  
  assert get_greatest_2([1, 5, 3, 7, 4, 7, 8, 9, 2, 10, 6, 8]) == (10, 9)
  assert get_greatest_2([1, 2]) == (2, 1)
  assert get_greatest_2([1]) == None
  assert get_greatest_2([]) == None
  assert get_greatest_2([3, 5, 6, 8, 7, 10, 9, 2, 1, 4]) == (10, 9)
  assert get_greatest_2([4, 2, 9, 1, 5]) == (9, 5)
  assert get_greatest_2([7, 7, 7, 7]) == (7, 7)
output: def get_greatest_2(items):
      if len(items) < 2:
          return None
      max1, max2 = float('-inf'), float('-inf')
      for item in items:
          if item > max1:
              max1, max2 = item, max1
          elif item > max2:
              max2 = item
      return max1, max2