      def peek(self):
          return self.top.data if self.top is not None else None
  
      def is_empty(self):
          return self.peek() is None 
</s> remove         return data </s> add  </s> remove     main() </s> add  </s> remove     main() </s> add  </s> remove     main() </s> add  </s> remove     main() </s> add 
      def peek(self):
          return self.top.data if self.top is not None else None
  
      def is_empty(self):

keep keep keep keep replace
 #273: Remove nose dependency for stacks_queues/ (#276) 
stacks_queues/stack/stack.py