old_contents: #!/usr/bin/python
  #
  # Copyright 2016 BMC Software, Inc.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  #
  class Animal(object):
  
      def __init__(self):
          self.voice = "???"
  
      def speak(self):
          print('A {0} says "{1}"'.format(self.__class__.__name__, self.voice))
  
  class Cat(Animal):
  
      def __init__(self):
          super(Cat, self).__init__()
          self.voice = 'Meow!'
  
  class Dog(Animal):
  
      def __init__(self):
          super(Dog, self).__init__()
          self.voice = 'Woof!'
  
  
  if __name__ == '__main__':
      animal = Animal()
      animal.speak()
  
      cat = Cat()
      cat.speak()
  
      dog = Dog()
      dog.speak()
  
new_contents: #!/usr/bin/python
  #
  # Copyright 2016 BMC Software, Inc.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  #
  class Animal(object):
  
      def __init__(self):
          self.voice = "???"
  
      def speak(self):
          print('{0} says "{1}"'.format(self.__class__.__name__, self.voice))
  
  class Cat(Animal):
  
      def __init__(self):
          super(Cat, self).__init__()
          self.voice = 'Meow!'
  
  class Dog(Animal):
  
      def __init__(self):
          super(Dog, self).__init__()
          self.voice = 'Woof!'
  
  
  if __name__ == '__main__':
      animal = Animal()
      animal.speak()
  
      cat = Cat()
      cat.speak()
  
      dog = Dog()
      dog.speak()
  
subject: Change speak() method