code: def delete_channel_cb(self, viewer, channel):
          
          chname_del = channel.name
          # TODO: delete thumbs for this channel!
          self.logger.debug("deleting thumbs for channel '%s'" % (chname_del))
          with self.thmblock:
              new_thumb_list = []
              un_hilite_set = set([])
              for thumbkey in self.thumb_list:
                  chname = thumbkey[0]
                  if chname != chname_del:
                      new_thumb_list.append(thumbkey)
                  else:
                      if thumbkey in self.thumb_dict:
                          del self.thumb_dict[thumbkey]
                      un_hilite_set.add(thumbkey)
  
              self.thumb_list = new_thumb_list
              self._tkf_highlight -= un_hilite_set  # Unhighlight
  
          self.fv.gui_do_oneshot('thumbs-reorder', self.reorder_thumbs)
docs: Called when a channel is deleted from the main interface.
          Parameter is channel (a bunch).