*   Add a `tf.distribute.cluster_resolver.TPUClusterResolver.connect` API to
    simplify TPU initialization.
*   Add `tf.distribute.Strategy.gather` and
    `tf.distribute.ReplicaContext.all_gather` methods to gather and concatenate
    `tf.distribute.DistributedValues` across workers and devices.

### `tf.keras`:

*   Introduces experimental preprocessing layers API

r  = float64(x*y) + z
r  = z; r += float64(x*y)
t  = float64(x*y); r = t + z
</pre>

<h4 id="String_concatenation">String concatenation</h4>

<p>
Strings can be concatenated using the <code>+</code> operator
or the <code>+=</code> assignment operator:
</p>

<pre>
s := "hi" + string(c)
s += " and good bye"
</pre>

<p>