* feat: add aliases for several series properties

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Co-authored-by: Tim Swast <[email protected]>

* feat: Allow passing index objects to df.drop

* remove notebook files

* add first implementation for df.drop(index)

* use index_columns property

* don't use _expr.keys()

* fix order bug and add test

* fix index names

* support multiindex

* remove accidentally added files

* add type hint

* remove debug print statements

* fix: fix df/series.iloc by list with multiindex

* complete merge

* remove unneeded isinstance

* refactor _drop_by_index

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Co-authored-by: Henry J Solberg <[email protected]>
Co-authored-by: Tim Swast <[email protected]>

* refactor: simplify ArrayValue public interface

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Co-authored-by: Tim Swast <[email protected]>

* feat: add equals methods to series/dataframe

* fix: change the invalid url in docs

* fix: address the comment

Source-Link: googleapis/synthtool@0c7b033
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:08e34975760f002746b1d8c86fdc90660be45945ee6d9db914d1508acdf9a547

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

* docs: add more preprocessing models into the docs menu.

* Trigger kokoro rebuild

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:
- [ ] Make sure to open an issue as a [bug/issue](https://togithub.com/googleapis/python-bigquery-dataframes/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
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- [ ] Code coverage does not decrease (if any source code was changed)
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Fixes #<issue_number_goes_here> 🦕

* feat: add iat indexers

* select_columns correction

* add iloc for tuples

* add dataframe tests

* add series tests

* add third party comments

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Co-authored-by: Henry J Solberg <[email protected]>

* feat: add level param to DataFrame.stack

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>