GitLab

* Fix unit tests failures.

* 96% of TF 2.0 tests on GPU are passing.

* Currently all passing GPU and CPU TF 2.0

* Address code comments.

* use tf 2.0 cast.

* Comment about working on TF 2.0 CPU

* Uses contrib turn off for TF 2.0.

* Fix wide_deep and add keras_common_tests.

* use context to get num_gpus.

* Switch to tf.keras.metrics

* Exemplify csv handing in serving for boosted_trees model by using custom built signature_def.

* some minor touches.

* Reverted back to using the file instead of module in the example.

* Make boosted_trees Garden-official

* Fix nits

* Add boosted_trees to the official models

* Comments addressed from review, and a test added; using absl.flags instead of argparser.

* Used help_wrap. Also added instructions for inference.