Adds a namespace anchor to physicsnemo's __init__ file

[coreyjadams]

PhysicsNeMo Pull Request

This allows extension packages and libraries to share the physicsnemo import path without an init file.

Relevant docs:
https://docs.python.org/3/library/pkgutil.html

Description

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• The CHANGELOG.md is up to date with these changes.
• An issue is linked to this pull request.
• If I am implementing a new model or modifying any existing model, I have followed the Models Implementation Coding Standards.

Dependencies

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CODEOWNERS review map

Current for commit 1656efa047cf. An approval covers every file listed for that owner; one owner is sufficient for shared files.

⏳ @coreyjadams — 1 file(s)

• test/core/test_namespace_anchor.py

No CODEOWNER

• physicsnemo/init.py

Comment /codeowners-info to refresh.

[greptile-apps]

The PR appears safe to merge, with the intended namespace-package behavior covered by a focused regression test.

Summary

This PR turns the existing physicsnemo package into a namespace anchor using pkgutil.extend_path, allowing separately installed distributions to contribute physicsnemo.<subpackage> portions while preserving existing top-level exports.

• Extends physicsnemo.__path__ before importing anchor submodules.
• Adds an isolated subprocess test proving that an additional package portion on sys.path is importable.
• Verifies that existing anchor attributes and version metadata remain available.

_{Reviews (1) · Last reviewed commit: "This adds a namespace anchor to physicsn..."}