MNT: Update type hints to modern Python 3.10+ syntax

[Copilot]

Completes the modernization of type hints started in #426, replacing legacy typing module constructs with built-in equivalents throughout the codebase.

Changes

• Optional[X] → X | None across all files
• Union[X, Y] → X | Y where applicable
• List[X] → list[X], Dict[K, V] → dict[K, V], Sequence[X] → list[X]
• Removed unused imports from typing (Optional, List, Sequence, Union, Dict) in 14 files
• Fixed a bug from MNT Improve typehints. #426 in _visualize.py where trusted was annotated as [str] | None (bare list literal) instead of list[str] | None

Type distinction in trusted parameter

Nodes in _general.py / _audit.py that internally pass type objects (e.g. dict, list, set) to _get_trusted use list[str | type[Any]] | None, while nodes in _numpy.py, _sklearn.py, etc. that only deal with string type names use list[str] | None.

Before / After

# Before
from typing import Any, Iterator, List, Literal, Optional, Sequence

def delete(self, key: str | Sequence[str]) -> None: ...
trusted: Optional[List[str]] = None

# After
from typing import Any, Iterator, Literal

def delete(self, key: str | list[str]) -> None: ...
trusted: list[str] | None = None

[adrinjalali]

@copilot CI is failing, please try to fix.

[Copilot]

@copilot CI is failing, please try to fix.

Fixed in 0ad3c09. The pre-commit ruff hook detected a missing blank line between stdlib imports (import pickle) and local imports (from skops.cli._utils) in _convert.py — caused by removing the from typing import Optional line without preserving the import group separator. Added the blank line back.

[adrinjalali]

@copilot please fix CI issues, until they're fixed.

[Copilot]

@copilot please fix CI issues, until they're fixed.

Fixed in a141218. Three issues were causing CI failures:

1. ruff F821: memoize: bool = True was accidentally removed from Node.__init__ — restored it.
2. mypy type errors: list[str | type[Any]] | None for trusted was incompatible with subclass list[str] | None values due to list invariance — changed to Sequence[str] | None in Node.__init__, CachedNode.__init__, get_tree, and _get_trusted; also fixed _general.py, _scipy.py, old/_general_v0.py, and _persist.py.
3. pixi.lock format: pixi v0.39.5 in CI normalizes the lock file (./ → ., removes options: pypi-prerelease-mode blocks, normalizes sys_platform strings) — applied those changes directly.

Warning

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• pixi.sh
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If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[adrinjalali]

@copilot CI still fails.

[Copilot]

@copilot CI still fails.

Fixed in f60698b. The remaining failure was a mypy error in _markup.py:269: dict[str, Sequence[Any]] is not compatible with TableSection's expected Mapping[str, list[Any]] because tuples from zip(*body) are Sequence but not list. Fixed by explicitly converting to lists: {key: list(val) for key, val in zip(columns, data_transposed)} and updating the annotation to Mapping[str, list[Any]].