input: Write a python function to check if a list is sorted in ascending order.
  assert is_sorted([1, 2, 3, 4, 5]) == True
  assert is_sorted([5, 4, 3, 2, 1]) == False
  assert is_sorted([10, 20, 30, 40, 50]) == True
  assert is_sorted([1, 3, 2, 4, 5]) == False
  assert is_sorted([]) == True
output: def is_sorted(lst):
      return lst == sorted(lst)