fix: lazy import utilities

[wyzula-jan]

Description

This PR fixes bec_lib.utils.import_utils.lazy_import_from() and makes the bec_lib.utils package import path lightweight.

lazy_import_from() now correctly supports both a single string and a sequence of strings. The previous implementation treated plain strings as iterables of characters and returned a one-shot generator for multi-name imports. The new implementation returns a single proxy for one name, a tuple of proxies for multiple names, and memoizes resolved attributes with init_once=True.

bec_lib.utils.__init__ now exposes public utility helpers lazily. This is needed because Python imports bec_lib.utils.__init__ before bec_lib.utils.import_utils, so the previous eager imports of scan_utils, rpc_utils, and threading_utils made importing the lazy import helper unnecessarily heavy.

Type of Change

• Fix lazy_import_from() string handling, multi-name return behavior, and proxy memoization.
• Make bec_lib.utils public exports lazy to avoid eager imports when importing bec_lib.utils.import_utils.
• Add regression tests for lazy import behavior and import boundaries.

[Copilot]

Pull request overview

This PR fixes and strengthens the library’s lazy-import behavior by preventing unintended imports triggered by bec_lib.utils package initialization and by making lazy_import_from more ergonomic/consistent.

Changes:

• Updated lazy_import_from to accept a single string name, return tuples for multi-name imports, and materialize proxies only once.
• Switched bec_lib.utils re-exports to a PEP 562 __getattr__-based lazy export mechanism to avoid importing heavier utilities at import time.
• Reworked tests to validate lazy import semantics and verify that importing bec_lib.utils.import_utils does not import scan_utils.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
bec_lib/tests/test_import_utils.py	Replaced prior tests with new coverage focused on lazy import behavior and import side effects.
bec_lib/bec_lib/utils/import_utils.py	Improved typing/behavior of lazy_import_from; moved inspect import inside isinstance_based_on_class_name.
bec_lib/bec_lib/utils/__init__.py	Implemented lazy re-exports via module __getattr__ to prevent eager imports of scan_utils/others.

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[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
bec_lib/bec_lib/utils/__init__.py	76.92%	2 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[wakonig]

bec_lib.utils.init now exposes public utility helpers lazily. This is needed because Python imports bec_lib.utils.init before bec_lib.utils.import_utils, so the previous eager imports of scan_utils, rpc_utils, and threading_utils made importing the lazy import helper unnecessarily heavy.

It is not like I don't agree with the changes but just out of curiosity: What exactly made it heavy in these imports? I would have thought functools should be quite fast

[wyzula-jan]

bec_lib.utils.init now exposes public utility helpers lazily. This is needed because Python imports bec_lib.utils.init before bec_lib.utils.import_utils, so the previous eager imports of scan_utils, rpc_utils, and threading_utils made importing the lazy import helper unnecessarily heavy.

It is not like I don't agree with the changes but just out of curiosity: What exactly made it heavy in these imports? I would have thought functools should be quite fast

import_utils previously triggered bec_lib.utils.init, which imported scan_utils, and scan_utils imports typeguard