input: Write a python function to find the three largest numbers from a list.
  assert max_three_nums([7, 9, 15, 10, 11])==[15, 11, 10]
  assert max_three_nums([1, 2, 3, 4, 5])==[5, 4, 3]
  assert max_three_nums([10, 10, 10, 10, 10])==[10, 10, 10]
  assert max_three_nums([100, -1, 50, 0, 25])==[100, 50, 25]
output: def max_three_nums(lst):
      return sorted(lst, reverse=True)[:3]