Sync instance-class-static-methods with the updated tutorial

[realpython-bot]

Companion-code sync for Python's Instance, Class, and Static Methods Demystified after this maintenance cycle.

• Update draft (source of truth): https://realpython.com/pbjt/blog/post/2324/change/
• Live article: https://realpython.com/instance-class-and-static-methods-demystified/
• Maintenance card: https://trello.com/c/p4U918WO

What changed

pizza.py — the Pizza.get_size_in_inches() static method had drifted from the tutorial's listing:

• Docstring restored to the article's wording: """Returns the diameter in inches for common pizza sizes.""" (the folder said "an approximate diameter in inches for common sizes").
• size_map re-expanded to the article's one-key-per-line literal with a trailing comma, instead of the collapsed one-liner.

What deliberately did not change

• demo.py already carried the colon on def static_method():, so this cycle's code-failure fix was article-only — no repo change needed.
• The version-bump from python==3.13 to python==3.14 touches no file here: the folder is pure standard library, so there is no requirements.txt or constraints.txt for a reader to install from and nothing to re-pin.
• The {% ref %} glossary links added this cycle are prose-only.
• The two LOW pedagogical findings (the "enforced by the Python runtime" wording and raising instead of returning "Unknown size") were left for a human, so get_size_in_inches() keeps its sentinel return.

How this was verified

• Fresh uv venv --python 3.14 (CPython 3.14.6), matching the draft's dependencies: python==3.14. No third-party packages are required.
• demo.py and pizza.py both executed (MPLBACKEND=Agg) — both run clean.
• Every code block and REPL session in the updated draft was replayed against these modules: all 22 expected outputs reproduce verbatim, including <demo.DemoClass object at 0x...>, <class 'demo.DemoClass'>, the TypeError: DemoClass.instance_method() missing 1 required positional argument: 'self' message, the Pizza([...]) reprs, the factory methods, and get_size_in_inches() returning 12, 8, and 16.
• Repo gates at the version pinned in the root requirements.txt (ruff==0.14.1): uvx ruff@0.14.1 format --check instance-class-static-methods → "2 files already formatted"; uvx ruff@0.14.1 check instance-class-static-methods → "All checks passed!".

Needs a human merge.