[ainuo-AI]

group_by() iterates mapping keys directly, unlike the other collection helpers. For example, group_by({'first': 1, 'second': 3}, parity) passes the strings 'first' and 'second' to a numeric callback, while the default iteratee produces groups of keys instead of values.

Group Mapping.values() with the existing loop. Add mapping-specific overloads and assert_type regressions, cover dict/UserDict/read-only MappingProxyType with identity, callable and shorthand iteratees, and add a dictionary example. Update the changelog and contributor list.

Validation on Windows / CPython 3.12.10:

• All 12 new runtime regressions fail on unchanged upstream and pass after this fix.
• Standard unit/doctest suite, using inv test's source/test ordering and exclusion of the legacy type-snapshot directory: 3336 passed, 100% coverage.
• The new assert_type regression runs separately with pytest-mypy-testing and passes.
• Ruff check/changed-file formatting, mypy over src/pydash, tests and tasks.py (30 files), and git diff --check pass.

The full supported interpreter/OS matrix was not run locally. AI assistance: OpenAI Codex was used for investigation, implementation and running the validation commands.

[dgilland]

Lint check is failing on mypy:

Running mypy
  tests/test_objects.py:342:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
  ERROR: src/pydash/chaining/all_funcs.pyi is out of date. Please run `inv generate-chaining-types` and commit the changes.
  PASSED
  
  Running chaining-types-update-required
  ERROR: linters failed: chaining-types-update-required
  FAILED