old_contents: 
  class MailState():
      _reading_data = False
  
      def set_reading(self, val):
          self._reading_data = val
  
      def get_reading(self):
          return self._reading_data
  
new_contents: class MailState():
      _reading_data = False
  
      def set_reading(self, val):
          self._reading_data = val
  
      @property
      def reading(self):
          return self._reading_data
  
subject: Change getter in to property