message: [tf.data] Fix typo in `Dataset.prefetch()` docstring.
diff: @@ -563,7 +563,7 @@ class Dataset(object):
  Args:
  buffer_size: A `tf.int64` scalar `tf.Tensor`, representing the
  - maximum number elements that will be buffered when prefetching.
  + maximum number of elements that will be buffered when prefetching.
  Returns:
  Dataset: A `Dataset`.
  