[BEAM-9561] Initial framework for testing pandas website docs.

[robertwb]

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Post-Commit Tests Status (on master branch)

Lang	SDK	Dataflow	Flink	Samza	Spark	Twister2
Go		---		---		---
Java
Python				---		---
XLang		---		---		---

Pre-Commit Tests Status (on master branch)

---	Java	Python	Go	Website	Whitespace	Typescript
Non-portable
Portable	---		---	---	---	---

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GitHub Actions Tests Status (on master branch)

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[robertwb]

R: @TheNeuralBit

[codecov]

Codecov Report

Merging #12819 into master will increase coverage by 0.13%.
The diff coverage is 96.22%.

@@            Coverage Diff             @@
##           master   #12819      +/-   ##
==========================================
+ Coverage   82.31%   82.44%   +0.13%     
==========================================
  Files         455      455              
  Lines       54596    54864     +268     
==========================================
+ Hits        44941    45233     +292     
+ Misses       9655     9631      -24     

Impacted Files	Coverage Δ
sdks/python/apache_beam/dataframe/doctests.py	96.75% <96.22%> (-0.45%)	⬇️
...dks/python/apache_beam/options/pipeline_options.py	93.76% <0.00%> (-1.03%)	⬇️
sdks/python/apache_beam/io/gcp/bigquery.py	80.08% <0.00%> (-0.63%)	⬇️
sdks/python/apache_beam/io/fileio.py	95.80% <0.00%> (-0.05%)	⬇️
...e_beam/portability/api/beam_runner_api_pb2_urns.py	100.00% <0.00%> (ø)
..._beam/runners/portability/sdk_container_builder.py	31.21% <0.00%> (ø)
...eam/testing/benchmarks/nexmark/nexmark_launcher.py	0.00% <0.00%> (ø)
...ache_beam/runners/interactive/recording_manager.py	98.90% <0.00%> (+0.02%)	⬆️
sdks/python/apache_beam/transforms/environments.py	83.73% <0.00%> (+0.19%)	⬆️
... and 12 more

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[robertwb]

Run Python PreCommit

[robertwb]

The apache_beam.transforms.ptransform_test.PTransformTest.test_flatten_no_pcollections failure looks unrelated.

[robertwb]

Run Python PreCommit

[robertwb]

Same test_flatten_no_pcollections failure.

[TheNeuralBit]

LGTM, just minor comments

[robertwb]

Run Python PreCommit

[robertwb]

Run Python PreCommit

[TheNeuralBit]

Failure looks like BEAM-10987