input: Write a function to calculate the total cost of items in a shopping list.
  assert total_cost([("apple", 2, 3), ("banana", 1, 1), ("orange", 5, 2)]) == 17
  assert total_cost([("milk", 3, 2.5), ("bread", 2, 2), ("butter", 1, 4)]) == 15.5
  assert total_cost([("pen", 10, 1.5), ("notebook", 5, 3.2)]) == 31
output: def total_cost(items):
      return sum(quantity * price for _, quantity, price in items)