input: Write a python function to create subarrays of a given size k from an input array.
  assert form_subarrays([1, 2, 3, 4, 5, 6, 7, 8], 3) == [[1, 2, 3], [4, 5, 6], [7, 8]]
  assert form_subarrays([10, 20, 30, 40, 50], 2) == [[10, 20], [30, 40], [50]]
  assert form_subarrays([5, 10, 15, 20, 25, 30], 4) == [[5, 10, 15, 20], [25, 30]]
output: def form_subarrays(arr, k):
      return [arr[i:i + k] for i in range(0, len(arr), k)]