Time: 0:00
Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).
This bug belongs to the type errors pattern
Totals that concatenate, sorts that put 10 before 9, comparisons that refuse to run.
What went wrong: list.append() adds its argument as a single element, creating a nested sublist when passed another list.
The fix: Use list.extend() to append each element of new_roles individually: roles.extend(new_roles)
Remember: In Python, append() adds an object as a single element; extend() concatenates another iterable.
The pattern behind it: type errors.
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