title: Python super() chain not advancing
body: <p>Python newbie here, would appreciate some help with multiple inheritance!</p>
  
  <p>Consider the following class hierarchy:</p>
  
  <pre><code>class Base1:
      def display(self):
          print('Base1')
  
  class Base2:
      def display(self):
          print('Base2')
  
  class Derived1 (Base1):
      def display(self):
          super().display()
          print('Derived1')
  
  class Derived2 (Base2):
      def display(self):
          super().display()
          print('Derived2')
  
  class Derived (Derived1, Derived2):
      def display(self):
          super().display()
          print('Derived')
  
  Derived().display()
  </code></pre>
  
  <p>I was expecting that the output of this would print the names of all the classes involved in the hierarchy, but it's not so. Further, if I add <code>super().display()</code> to both <code>Base1</code> and <code>Base2</code>, I get the error <code>AttributeError: 'super' object has no attribute 'display'</code>.</p>
  
  <p>What's wrong?</p>