[tf.data] Export `tf.data.experimental.AUTOTUNE`.

PiperOrigin-RevId: 216890862

tensorflow/python/data/experimental/__init__.py

@@ -57,6 +57,8 @@ See [Importing Data](https://tensorflow.org/guide/datasets) for an overview.
 @@StatsAggregator
 @@unbatch
 @@unique
+
+@@AUTOTUNE
 """
 
 from __future__ import absolute_import

tensorflow/python/data/experimental/ops/optimization.py

@@ -21,9 +21,12 @@ from tensorflow.python.data.ops import dataset_ops
 from tensorflow.python.framework import dtypes
 from tensorflow.python.framework import ops
 from tensorflow.python.ops import gen_experimental_dataset_ops
+from tensorflow.python.util.tf_export import tf_export
+
 
 # A constant that can be used to enable auto-tuning.
 AUTOTUNE = -1
+tf_export("data.experimental.AUTOTUNE").export_constant(__name__, "AUTOTUNE")
 
 
 # TODO(jsimsa): Support RE matching for both individual transformation (e.g. to

tensorflow/tools/api/golden/v1/tensorflow.data.experimental.pbtxt

 path: "tensorflow.data.experimental"
 tf_module {
+  member {
+    name: "AUTOTUNE"
+    mtype: "<type \'int\'>"
+  }
   member {
     name: "CheckpointInputPipelineHook"
     mtype: "<type \'type\'>"

tensorflow/tools/api/golden/v2/tensorflow.data.experimental.pbtxt

 path: "tensorflow.data.experimental"
 tf_module {
+  member {
+    name: "AUTOTUNE"
+    mtype: "<type \'int\'>"
+  }
   member {
     name: "CheckpointInputPipelineHook"
     mtype: "<type \'type\'>"