code: def get_tags(self, intersection=False):
          
          tags = set(list(self._tags))
          if intersection:
              for m in self.get_messages().keys():
                  tags = tags.intersection(set(m.get_tags()))
          return tags
docs: returns tagsstrings attached to this thread
  
          :param intersection: return tags present in all contained messages
                               instead of in at least one (union)
          :type intersection: bool
          :rtype: set of str