input: Write a python function to optimize shipping cost based on the weight of items.
  assert optimize_shipping_cost([{'weight': 2, 'cost': 10}, {'weight': 3, 'cost': 5}]) == 2
  assert optimize_shipping_cost([{'weight': 7, 'cost': 15}, {'weight': 4, 'cost': 10}]) == 4.4
  assert optimize_shipping_cost([{'weight': 3, 'cost': 5}, {'weight': 6, 'cost': 8}, {'weight': 8, 'cost': 12}]) == 10.5
output: def optimize_shipping_cost(items):
      total_weight = sum(item['weight'] for item in items)
      total_cost = sum(item['cost'] for item in items)
      return total_cost / total_weight