Events are [item, change] (positive = received, negative = sold). Write stock_after(events) returning item → final stock, dropping items whose stock is 0.
stock_after([['pen', 10], ['book', 2], ['pen', -10], ['book', 1]])
→ {'book': 3}stock_after([])
→ {}Submit runs 3 tests, including hidden edge cases.
Run your code to see the output here.