old_contents: from __future__ import absolute_import
  
  from .core import (ChannelDone, Channel, ReadChannel, MapChannel, FlatMapChannel,
                     FilterChannel, FutureChannel, ReadyFutureChannel, TeeChannel,
                     ProducerChannel, IterChannel, ZipChannel, CoGroupChannel,
                     WindowChannel, GroupChannel)
  
new_contents: from __future__ import absolute_import
  
  from .core import (
          Channel,
          ChannelDone,
          CoGroupChannel,
          FilterChannel,
          FlatMapChannel,
          FutureChannel,
          GroupChannel,
          IterChannel,
          MapChannel,
          ProducerChannel,
          ReadChannel,
          ReadyFutureChannel,
          TeeChannel,
          WindowChannel,
          ZipChannel)
  
  
subject: Change to one package per line for channel import