code: def have_thumbnail(self, fitsimage, image):
          
          chname = self.fv.get_channel_name(fitsimage)
  
          # Look up our version of the thumb
          idx = image.get('idx', None)
          path = image.get('path', None)
          if path is not None:
              path = os.path.abspath(path)
              name = iohelper.name_image_from_path(path, idx=idx)
          else:
              name = 'NoName'
  
          # get image name
          name = image.get('name', name)
  
          thumbkey = self.get_thumb_key(chname, name, path)
          with self.thmblock:
              return thumbkey in self.thumb_dict
docs: Returns True if we already have a thumbnail version of this image
          cached, False otherwise.