input: Write a python function to find the minimum and maximum numbers in a list and return them in a new list.
  assert get_min_max([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == [1, 10]
  assert get_min_max([10, 20, 45, 67, 84, 93]) == [10, 93]
  assert get_min_max([5, 7, 9, 8, 6, 4, 3]) == [3, 9]
output: def get_min_max(lst):
      if not lst:
          return []
      min_num = min(lst)
      max_num = max(lst)
      return [min_num, max_num]