text: '''
  Interfaces for IO
  '''
  
  
  class FrameSequence:
      '''Frame sequence interface'''
  
      def __next__(self):
          '''Returns next frame (along with its frame number)'''
          raise NotImplementedError
  
      def __iter__(self):
          return self
  
      def is_open(self):
          '''Returns if the sequence is open for reading more frames'''
          raise NotImplementedError
  
      def is_done(self):
          '''Returns if the sequence is over'''
          raise NotImplementedError
  
      def stop(self):
          '''Stop serving more frames'''
          raise NotImplementedError
  