title: unsupported operand type(s) for +: 'method' and 'float'
body: <pre><code>class Coffee:
      def __init__(self):
          self._price=4.0
  
      def price(self):
          return self._price
  
  
      def __str__(self):
          return "Coffee with price "+ str(self._price)
  
  
  class CoffeeWithMilk:
      def __init__(self, coffee):
          self.price+=coffee.price+0.5
  
      def price(self):
          return self.price
  
  
  coffee=Coffee()
  
  x=CoffeeWithMilk(coffee)
  coffeeWithMilk=CoffeeWithMilk(x)
  print(coffeeWithMilk)
  </code></pre>
  
  <p>How to fix this? Thanks</p>