* feat: add `DataFrames.corr()` method

* support multi-indices

* fix mypy

* support non-numeric col

* fix doc

* fix system 3.9

* fix doctest

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Fixes #312729021 🦕

To be more like sklearn, and make API more accurate. Those param shouldn't be called through positions.

* deps: add minimum version constraint for sqlglot to 19.9.0

This shouldn't be necessary, as sqlglot is only used as a transitive
dependency through ibis-framework, but in setting the constraints, we
can have greater assurance that sqlglot is upgraded alongside bigframes
in existing environments.

* formatting

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Towards internal issue 322845272 🦕

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Fixes internal issue 312304785 🦕

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Fixes #<issue_number_goes_here> 🦕

Release-As: 0.22.0

* k-means code sample

* formatting

* added test

* docs: add code sampke for creating kmeans model

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* Update samples/snippets/create_kmeans_model_test.py

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* code corrections resolved

* code corrections commit 1

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* explantions revised for clarity

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* code corrections

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* column wrapping

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* Update samples/snippets/create_kmeans_model_test.py

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* predict function added to tutorial

* replaced project_id with model_id

* reformatting

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