message: [tf.data] Reflect `MakeIterator` signature change in documentation.
diff: @@ -45,7 +45,7 @@ Each of these implementations comprises three related classes:
  * A `tensorflow::GraphDatasetBase` subclass (e.g. `TextLineDatasetOp::Dataset`),
  which represents the *immutable* definition of the dataset itself, and tells
  TensorFlow how to construct an iterator object over that dataset, in its
  - `MakeIterator()` method.
  + `MakeIteratorInternal()` method.
  * A `tensorflow::DatasetIterator<Dataset>` subclass (e.g.
  `TextLineDatasetOp::Dataset::Iterator`), which represents the *mutable* state
  @@ -103,7 +103,7 @@ class MyReaderDatasetOp : public DatasetOpKernel {
  public:
  Dataset(OpKernelContext* ctx) : GraphDatasetBase(ctx) {}
  - std::unique_ptr<IteratorBase> MakeIterator(
  + std::unique_ptr<IteratorBase> MakeIteratorInternal(
  const string& prefix) const override {
  return std::unique_ptr<IteratorBase>(
  new Iterator({this, strings::StrCat(prefix, "::MyReader")}));
  