message: Make example code runnable
diff: @@ -572,7 +572,7 @@ def angle(input, name=None):
  For example:
  ```
  - # tensor 'input' is [-2.25 + 4.75j, 3.25 + 5.75j], in `complex64` format
  +input = tf.constant([-2.25 + 4.75j, 3.25 + 5.75j])
  tf.angle(input) ==> array([2.0131705, 1.056345 ], dtype=float32)
  ```
  