input: Write a python function to calculate the total cost of two items and shipping charges.
  assert calculate_cost(10, 20, 15) == 45
  assert calculate_cost(5, 25, 10) == 40
  assert calculate_cost(100, 200, 50) == 350
output: def calculate_cost(item1, item2, shipping):
      return item1 + item2 + shipping