message: changed to doc-test format
diff: @@ -38,11 +38,15 @@ def to_categorical(y, num_classes=None, dtype='float32'):
  last.
  Usage Example:
  - ```python
  - import tensorflow as tf
  - y = [0, 2, 4, 3, 5, 0, 1, 1, 2]
  - tf.keras.utils.to_categorical(y, 6)
  - ```
  + >>> y = [0, 1, 2, 3, 3, 1, 0]
  + >>> tf.keras.utils.to_categorical(y, 4)
  + array([[1., 0., 0., 0.],
  + [0., 1., 0., 0.],
  + [0., 0., 1., 0.],
  + [0., 0., 0., 1.],
  + [0., 0., 0., 1.],
  + [0., 1., 0., 0.],
  + [1., 0., 0., 0.]], dtype=float32)
  Raises:
  Value Error: If input contains string value
  