[yaml] Add Beam YAML Examples and Getting started docs

[Polber]

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[Polber]

R: @robertwb

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[robertwb]

This is looking pretty good.

Let's remove the docs changes as we're moving those to the site and get these examples in.

[robertwb]

Any update on this?

[Polber]

@robertwb All comments addressed and rebased on master

[robertwb]

Only minor comments, then LGTM.

[robertwb]

Now that they're live, let's point to the official docs on https://beam.apache.org/documentation/sdks/yaml/

[Polber]

I pointed to UDF section since that is where MapToFields lives

[robertwb]

Perhaps intersperse these comments with the code itself?

[Polber]

@robertwb I refactored the example a bit to make it follow the logic more semantically. It also outputs Row(word=..., count=...) instead of Row(output="word: count")

Let me know what you think

[robertwb]

Looks good once we fix the failing tests and missing license headers.

[robertwb]

Looks like you need to add an apache license preamble to sdks/python/apache_beam/yaml/examples/README.md to make RAT happy.

[Polber]

Looks like you need to add an apache license preamble to sdks/python/apache_beam/yaml/examples/README.md to make RAT happy.

Are the other tests known issues? I don't see how my PR is affecting huggingface and rowcoder tests

[kennknowles]

Perhaps rebasing will get to green if there were issues on master?

[robertwb]

I kicked off some re-runs, but I'm not sure if it always rebases on head. +1 to merging with master and re-pushing if this doesn't get things green.

[kennknowles]

I think it does not. The various merge and HEAD commits associated with a PR are, I think, only updated when the head commit of the PR changes. So reruns will be against the same commit. (I could have this wrong, of course)

[Polber]

@robertwb

Finally got the tests green.

The RowCoderTest imports beam, which imports the examples_test.py file I added, which used to import main.py. In main.py, there is the line LogicalType.register_logical_type(MillisInstant) - This overrided the MicrosInstant that RowCoderTest requires to pass.

I adjusted the test to run yaml_transform.expand_pipeline instead, which fixed that issue. I also realized that the examples tests were not actually running on presubmits, so I added several fixes to get them running and green.

[robertwb]

Thanks. Nice to finally get this in.