[pabszero]

An empty Index currently compares equal to an empty list or string, while comparisons with None or a same-length nonempty list raise TypeError/AttributeError. Return NotImplemented for non-mappings in both equality methods, allowing Python to try the other operand's reflected comparison.

Fixes #387. Preserve the existing order-sensitive Index/OrderedDict comparisons and order-insensitive general mapping comparisons. This is independent of #378, which addresses missing-key sentinel collisions between mappings.

Validation on Windows:

• New comparison cases: 17 failures and 4 passing mapping controls before the fix; all 21 pass afterward. They cover empty/populated Index objects, both operand orders, equality/inequality, reflected methods and mapping order.
• Full suite including tutorial doctests: 272 tests and 12 subtests pass on both CPython 3.12.14 and 3.13.5; 99.04% branch-aware coverage (98% required).
• Blue, isort and Flake8 7.4.1 pass on changed files; mypy and Pylint 2.17.7 pass on all library modules (Pylint on Python 3.12). git diff --check passes. Published source/test bytes match the tested files.
• Test runs report Django USE_L10N deprecation warnings; Python 3.12 uses coverage's Python tracer fallback, and Python 3.13 also reports SQLite ResourceWarnings from the existing suite. Other platforms/versions and hosted CI are unverified.

Found through code inspection and prepared/tested with OpenAI Codex assistance under the account owner's OSS contribution request. No production incident or independent human review is claimed.