message: refine dataset prefetch comments
diff: @@ -700,11 +700,10 @@ class DatasetV2(tracking_base.Trackable, composite_tensor.CompositeTensor):
  """Creates a `Dataset` that prefetches elements from this dataset.
  Note: Like other `Dataset` methods, prefetch operates on the
  - elements of the dataset. It has no concept of examples vs. batches.
  + elements of the input dataset. It has no concept of examples vs. batches.
  `examples.prefetch(2)` will prefetch two elements (2 examples),
  while `examples.batch(20).prefetch(2)` will prefetch 2 elements
  - (2 batches, of 20 examples each). The typical use-case is to
  - `prefetch` batches.
  + (2 batches, of 20 examples each).
  Args:
  buffer_size: A `tf.int64` scalar `tf.Tensor`, representing the maximum
  