message: fix the range arg explanation and improve readability
diff: @@ -887,9 +887,9 @@ class DatasetV2(tracking_base.Trackable, composite_tensor.CompositeTensor):
  Args:
  *args: follows the same semantics as python's xrange.
  - len(args) == 1 -> start = 0, stop = args[0], step = 1
  - len(args) == 2 -> start = args[0], stop = args[1], step = 1
  - len(args) == 3 -> start = args[0], stop = args[1, stop = args[2]
  + len(args) == 1 -> start = 0, stop = args[0], step = 1.
  + len(args) == 2 -> start = args[0], stop = args[1], step = 1.
  + len(args) == 3 -> start = args[0], stop = args[1], step = args[2].
  **kwargs:
  - output_type: Its expected dtype. (Optional, default: `tf.int64`).
  