old_contents: 
  
  class Extension:
      def __init__(self, **kwargs):
          self.app = kwargs.get('app')
          self._initialized = False
  
      def initialize(self, app):
          self.app = app
          self._initialized = True
  
      @property
      def initialized(self):
          return self._initialized
  
  
new_contents: class Extension:
      def __init__(self, **kwargs):
          self.app = kwargs.get('app')
          if self.app is not None:
              self._initialized = True
          else:
              self._initialized = False
  
      def initialize(self, app):
          self.app = app
          self._initialized = True
  
      @property
      def initialized(self):
          return self._initialized
  
  
subject: fix _initialized bug