text: from interface_tv import ITv
  
  class CrtTv(ITv):
      def __init__(self):
          pass
      
      def display(self,channel):
          print('ブラウン管：', end='')
          if self.__region == '新潟':
              if channel == 8:
                  print('NHK総合表示中...')
              elif channel == 12:
                  print('NHK教育表示中...')
              else:
                  print('表示できません...')
          else:
              print('表示できません')    
      
      
      @property
      def region(self):
          return self.__region
          
      
      @region.setter
      def region(self,value):
          self.__region = value
      
  
  def main():
      assert issubclass(CrtTv().__class__, ITv)
      assert isinstance(CrtTv(), ITv)
      
      tv = CrtTv()
      tv.region = '新潟'
      tv.display(8)
  
  
  if __name__ == '__main__':
      main()
  