input: Write a function to find the greatest 2 numbers from a list of integers. The function should return a tuple containing these two numbers in descending order.
  
  def get_greatest_2(items):
      max1 = max2 = 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, -5, -3, -7, -4, -7, -8, -9, -2, -10, -6, -8]) == (-1, -2)
  assert get_greatest_2([1]) == (1, float('-inf'))
  assert get_greatest_2([]) == (float('-inf'), float('-inf'))
output: def get_greatest_2(items):
      max1 = max2 = float('-inf')
      for item in items:
          if item > max1:
              max1, max2 = item, max1
          elif item > max2:
              max2 = item
      return max1, max2