Fixed schema related issues for census example.

[pritamdodeja]

Summary of Changes

It appears some of the schema related functionality was pointing to old locations, which was causing census_example_v2.py to break. This pull request fixes these schema related issues and makes it so that census_example_v2.py now works with

python census_example_v2.py --input_data_dir data --working_dir working_area

Details

dataset_metadata has been replaced by schema_utils in imports and
RecordBatchToExamplesEncoder is now imported from tfx_bsl.coders.example_coder.
schema_from_feature_spec is now being called from schema_utils, and
RecordBatchToExamplesEncoder is now passed the schema, which was missing
earlier.
_RAW_DATA_METADATA schema creation also fixed by pointing it to
schema_utils.from_feature_spec. The net result is census_example_v2.py
now works as expected.

[zoyahav]

Were you testing it previously against tfx_bsl's master branch or just a specific release of it? (similarly for the tensorflow_transform version)
Note that these examples are tested continuously against the latest master branch versions.

Using dataset_metadata.DatasetMetadata.from_feature_spec is actually correct, it was introduced after the latest release of tensorflow_transform, see https://github.com/tensorflow/transform/blob/master/RELEASE.md#major-features-and-improvements.
Similar story for tfx_bsl.public.tfxio.RecordBatchToExamplesEncoder - https://github.com/tensorflow/tfx-bsl/blob/93743faf28953a8b32780d45eb3014f525f5cb5d/tfx_bsl/public/tfxio/__init__.py#L22.
Its schema argument is also optional, did you see a need to pass schema to RecordBatchToExamplesEncoder?

[pritamdodeja]

Thanks for your feedback. I was working through a lab for this course, and some of tft's functionality appeared broken in qwiklabs, so I came to this repo to understand better. I'm going to rebuild my environment so I can get these examples to run without issue, and go back to that class to see if I can figure out why things weren't working as expected. Thank you!

[pritamdodeja]

Everything works as expected after re-installing tensorflow-transform, apache-beam[gcp], pyarrow, tensorflow-metadata, and tfx-bsl to match exact versions listed on support matrix. Thank you!