code: def clicked(self, event):
          
          group = event.artist._mt_group
          n = event.artist._mt_n
          dt = num2date(event.artist._mt_bin)
          print("%4i %s events in %s sec beginning at %s"
                % (n, group, self.bucketsize, dt.strftime("%b %d %H:%M:%S")))
docs: Print group name and number of items in bin.