message: Add a testable example to tf.math.log
diff: @@ -7,4 +7,18 @@ op {
  name: "log"
  deprecation_version: 2
  }
  + description: <<END
  +I.e., \\(y = \log_e x\\).
  +
  +Example:
  +
  +```python
  +>>> x = tf.constant([0, 0.5, 1, 5])
  +>>> tf.math.log(x)
  +<tf.Tensor: shape=(4,), dtype=float32, numpy=array([ -inf, -0.6931472, 0. , 1.609438 ], dtype=float32)>
  +
  +```
  +
  +See: https://en.wikipedia.org/wiki/Logarithm
  +END
  }
  