chore(migration): Migrate code from googleapis/python-db-dtypes-pandas into packages/db-dtypes

[parthea]

See #11017.

This PR should be merged with a merge-commit, not a squash-commit, in order to preserve the git history.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on migrating the db-dtypes library into the main repository, setting up essential configurations for code quality, contribution guidelines, issue handling, and automated testing. It ensures the project is well-structured, maintainable, and adheres to Google's open-source standards.

Highlights

• Code Migration: Migrated the db-dtypes code from the googleapis/Python-db-dtypes-pandas repository into the packages/db-dtypes directory within the main repository.
• Git History Preservation: Ensured that the git history is preserved during the migration by recommending a merge-commit strategy.
• New File Additions: Added numerous configuration files, including .coveragerc, .flake8, CODEOWNERS, CONTRIBUTING.md, issue templates, pull request templates, auto-label configurations, blunderbuss settings, header checker linting, and various workflow configurations for compliance, docs, linting, and unit testing.
• Kokoro Build Configuration: Integrated Kokoro build configurations for continuous integration, pre-submit checks, and sample testing across multiple Python versions.

Activity

• The primary activity is the migration of the db-dtypes library from a separate repository into the main repository.
• Addition of various configuration files to support code quality, issue handling, and automated testing.
• Configuration of Kokoro build system for continuous integration and testing.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request migrates the db-dtypes package into this monorepo. The changes include source code, documentation, and a large number of configuration files for CI/CD and development tooling.

Overall, the migration looks solid. I've found a couple of minor issues:

• The CONTRIBUTING.rst file contains outdated information about supported Python versions.
• The extract_runtime_version helper function in _versions_helpers.py could be written more concisely.

I've left specific comments with suggestions for these points. After addressing them, this PR should be good to go.

[gemini-code-assist]

The supported Python versions listed in this file are inconsistent with the project's configuration (setup.py requires >=3.9). Please update the file to reflect that support starts from Python 3.9.

Specifically:

• This line should list versions from 3.9 onwards.
• The list of supported versions around line 224 should not include 3.7 and 3.8.
• The statement on line 248 should mention that support begins with version 3.9.

Suggested change

	- The feature must work fully on the following CPython versions:
	3.8, 3.9, 3.10, 3.11, 3.12, 3.13 and 3.14 on both UNIX and Windows.
	- The feature must work fully on the following CPython versions:
	3.9, 3.10, 3.11, 3.12, 3.13 and 3.14 on both UNIX and Windows.

[gemini-code-assist]

This function can be implemented more concisely by directly returning the components from sys.version_info. This improves readability and reduces verbosity. The docstring has also been updated to be more descriptive.

Suggested change

	def extract_runtime_version() -> Tuple[int, int, int]:
	# Retrieve the version information
	version_info = sys.version_info
	# Extract the major, minor, and micro components
	major = version_info.major
	minor = version_info.minor
	micro = version_info.micro
	# Display the version number in a clear format
	return major, minor, micro
	def extract_runtime_version() -> Tuple[int, int, int]:
	"""Extracts the runtime Python version as a tuple."""
	return sys.version_info.major, sys.version_info.minor, sys.version_info.micro