input: Write a python function to calculate the total cost of items in a list of tuples.
  assert total_cost([("apple", 2.50), ("banana", 3.00), ("avocado", 1.80)]) == 7.30
  assert total_cost([("bread", 1.00), ("milk", 2.50), ("eggs", 3.20)]) == 6.70
  assert total_cost([("water", 0.90), ("soda", 1.20), ("juice", 2.50)]) == 4.60
output: def total_cost(items):
      return sum(price for item, price in items)