code: def choose_existing_channel(self):
          
  
          if self.current.task_data.get('msg', False):
              self.show_warning_messages()
  
          _form = ChannelListForm()
          _form.title = _(u"Choose a Channel Which Will Be Merged With Chosen Channels")
  
          for channel in Channel.objects.filter(typ=15).exclude(
                  key__in=self.current.task_data['chosen_channels']):
              owner_name = channel.owner.username
              _form.ChannelList(choice=False, name=channel.name, owner=owner_name,
                                key=channel.key)
  
          _form.choose = fields.Button(_(u"Choose"))
          self.form_out(_form)
docs: It is a channel choice list and chosen channels
          at previous step shouldn't be on the screen.