code: def remove_tags(self, tags, afterwards=None):
          
          rmtags = set(tags).intersection(self._tags)
          if rmtags:
  
              def myafterwards():
                  self._tags = self._tags.difference(tags)
                  if callable(afterwards):
                      afterwards()
              self._dbman.untag('thread:' + self._id, tags, myafterwards)
              self._tags = self._tags.difference(rmtags)
docs: remove `tags` (list of str) from all messages in this thread
  
          .. note::
  
              This only adds the requested operation to this objects
              :class:`DBManager's <alot.db.DBManager>` write queue.
              You need to call :meth:`DBManager.flush <alot.db.DBManager.flush>`
              to actually write out.
  
          :param tags: a list of tags to be added
          :type tags: list of str
          :param afterwards: callback that gets called after successful
                             application of this tagging operation
          :type afterwards: callable