Tfx-bsl

Major Features and Improvements

* Introduced TFXIO, the interface for
[Standardized TFX Inputs](https://github.com/tensorflow/community/blob/master/rfcs/20191017-tfx-standardized-inputs.md)

* Added the first implementation of TFXIO, for tf.Example on TFRecords.

Bug Fixes and Other Changes

* Added a test_util sub-package that contains a tool to discover and run all
the absltests in a dir (like python's unittest discovery).
* Requires `apache-beam>=2.17,<3`
* Requires `pyarrow>=0.15,<0.16`
* Requires `tensorflow>=1.15,<3`
* Requires `tensorflow-metadata>=0.21,<0.22`.

Breaking Changes

Deprecations

Major Features and Improvements

* Requires `apache-beam>=2.16,<2.17` as 2.17 requires a pyarrow version
that we don't support yet.

Bug Fixes and Other Changes

Breaking Changes

* Behavior of csv_decoder.ColumnTypeInferrer was changed. A new column type,
`ColumnType.UNKNOWN` was added to denote that the inferrer could not
determine the type of that column (instead of making a guess of FLOAT).
Summary of behavior change (values in the examples are from the same
column):

+ `<int>, <empty>`: before: `FLOAT`; after: `INT`
+ `<empty>, ... , <empty>`: before: `FLOAT`; after: `UNKNOWN`

Deprecations

Major Features and Improvements

* Added a (beam) utility to infer column types from a `PCollection[CSVLine]`.
* Added a utility to parse a CSVLine into cells (conforming to RFC4180).

Bug Fixes and Other Changes

Breaking Changes

Deprecations

Major Features and Improvements

* Added dependency on `tensorflow>=1.15,<2.2`. Starting from 1.15, package
`tensorflow` comes with GPU support. Users won't need to choose between
`tensorflow` and `tensorflow-gpu`.
* Caveat: `tensorflow` 2.0.0 is an exception and does not have GPU
support. If `tensorflow-gpu` 2.0.0 is installed before installing
`tfx-bsl`, it will be replaced with `tensorflow` 2.0.0. Re-install
`tensorflow-gpu` 2.0.0 if needed.
* Added dependency on `tensorflow-serving-api>=1.15,<3`.
* Added a python PTransform, `tfx_bsl.beam.RunInference` that enables batch
inference.

Bug Fixes and Other Changes

Breaking Changes

Deprecations

Major Features and Improvements

* Added a tf.Example <-> Arrow coder.
* Added a tf.Example -> `Dict[str, np.ndarray]` coder (this is a legacy format
used by some TFX components).
* Added some common Arrow utilities (`tfx_bsl.arrow.array_util`).
* Added a python class, `tfx_bsl.beam.Shared` that helps sharing a single
instance of object across multiple threads.
* Added dependency on `apache-beam[gcp]>=2.16,<3`.
* Added dependency on `tensorflow-metadata>=0.15,<0.16`.

Bug Fixes and Other Changes

Breaking Changes

Deprecations