message: Updated flat_map doc example
diff: @@ -1028,12 +1028,10 @@ class DatasetV2(object):
  dataset of their elements:
  ```python
  - # NOTE: The following examples use `{ ... }` to represent the
  - # contents of a dataset. '[...]' represents a tensor.
  - a = {[1,2,3,4,5], [6,7,8,9], [10]}
  + a = Dataset.from_tensor_slices([ [1, 2, 3], [4, 5, 6], [7, 8, 9] ])
  - a.flat_map(lambda x: Dataset.from_tensor_slices(x)) ==
  - {[1,2,3,4,5,6,7,8,9,10]}
  + a.flat_map(lambda x: Dataset.from_tensor_slices(x + 1)) # ==>
  + # [ 2, 3, 4, 5, 6, 7, 8, 9, 10 ]
  ```
  `tf.data.Dataset.interleave()` is a generalization of `flat_map`, since
  