input: Write a python function to check if an array is sorted, and if not, sort the array.
  assert is_sorted([1, 2, 3, 4, 5]) == True
  assert is_sorted([5, 4, 3, 2, 1]) == [1, 2, 3, 4, 5]
  assert is_sorted([3, 1, 4, 2, 5]) == [1, 2, 3, 4, 5]
output: def is_sorted(arr):
      if arr == sorted(arr):
          return True
      else:
          return sorted(arr)