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: plain objects have no length, so settings.length is undefined.
The fix: return Object.keys(settings).length;
Remember: Object.keys(obj) gives an array of keys, and arrays have a length.
The pattern behind it: null and undefined errors.
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