Time: 0:00
Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).
This bug belongs to the null and undefined errors pattern
Cannot read properties of undefined, NoneType has no attribute, NaN appearing from nowhere.
What went wrong: scores.get("b") returns None, and sum() cannot add None to a number.
The fix: return sum(scores.get(n, 0) for n in names)
Remember: .get(key) gives None for a missing key. Pass a default of the right type.
The pattern behind it: null and undefined errors.
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