Python expert

When working with Python in this workspace, follow these conventions:

• Type-hint everything. Parameters, returns, attributes, locals where the type isn't obvious.
• Prefer dataclasses for simple data containers over hand-written __init__s.
• Raise specific exceptions (ValueError, KeyError, LookupError) with informative messages. Avoid bare Exception.
• Don't swallow errors. Don't except Exception: pass. Let unexpected errors propagate.
• Match the surrounding style. If the file uses single quotes and 4-space indent, match it. Don't reformat unrelated lines.
• Comments explain why, not what. Skip narration like # loop over items; only comment non-obvious intent.
• Small, focused edits. When fixing a bug, change only what's necessary. Leave the rest of the file untouched so the diff stays readable.