[ENH] Add exclude_tags parameter to all_objects #521

[direkkakkar319-ops]

Reference Issues/PRs

Fixes #521

What does this implement/fix? Explain your changes.

all_objects had a filter_tags parameter to include objects by tag
but no symmetric exclude_tags to filter them out. This PR adds that.

3 localized changes in skbase/lookup/_lookup.py:

• Line 755 (signature) — added exclude_tags=None parameter
• Lines 822-834 (docstring) — added parameter docs and usage examples
• Lines 947-953 (logic) — added exclusion filter reusing the existing
  _filter_by_tags function with inverted matching — clean and minimal

5 new tests added in skbase/tests/test_lookup.py:

• test_exclude_tags_none_is_noop — exclude_tags=None returns all objects
• test_exclude_tags_empty_dict_is_noop — exclude_tags={} returns all objects
• test_exclude_tags_excludes_matching — correctly excludes by tag value
• test_exclude_tags_combined_with_filter_tags — filter_tags + exclude_tags
  work together correctly
• test_exclude_tags_multiple_conditions — multiple tag conditions work as conjunction

No changes needed to skbase/lookup/__init__.py (already re-exports
all_objects directly) or get_package_metadata (different interface).

Does your contribution introduce a new dependency? If yes, which one?

No new dependencies introduced.

What should a reviewer concentrate their feedback on?

• The inverted _filter_by_tags logic at lines 947-953 — is this the
  cleanest way to implement exclusion or would a separate helper be preferred?
• The 5 new tests — are there any edge cases missing that should be covered?
• Docstring examples — are they clear and consistent with existing examples
  in the file?

Any other comments?

• black — passes
• flake8 — 0 errors
• pytest — all 6 tests pass (1 existing + 5 new)

The implementation is intentionally minimal and localized to _lookup.py
only, reusing the existing _filter_by_tags helper rather than introducing
any new logic.

PR checklist

For all contributions

• I've reviewed the project documentation on contributing
• I've added myself to the list of contributors.
• The PR title starts with either [ENH], [CI/CD], [MNT], [DOC], or [BUG] indicating whether
  the PR topic is related to enhancement, CI/CD, maintenance, documentation, or a bug.

For code contributions

• Unit tests have been added covering code functionality
• Appropriate docstrings have been added (see documentation standards)
• New public functionality has been added to the API Reference

[direkkakkar319-ops]

Hey, @fkiraly @felipeangelimvieira I'm a new contributor in this org and just raised this PR for Issue #521
Would love it if someone could review it when they get a chance. Thanks.