deprecated and will be removed in a future release.
    *   Metrics update and collection logic in default `Model.train_step()` is
        now customizable via overriding `Model.compute_metrics()`.
    *   Losses computation logic in default `Model.train_step()` is now
        customizable via overriding `Model.compute_loss()`.

  let description = [{
A one-shot iterator bundles the logic for defining the dataset and
the state of the iterator in a single op, which allows simple input
pipelines to be defined without an additional initialization
("MakeIterator") step.

One-shot iterators have the following limitations:

* They do not support parameterization: all logic for creating the underlying