code: def show_help_text(self, name, help_txt, wsname='right'):
          
          tabname = 'HELP: {}'.format(name)
          group = 1
          tabnames = self.ds.get_tabnames(group)
          if tabname in tabnames:
              # tab is already up somewhere
              return
  
          vbox = Widgets.VBox()
          vbox.set_margins(4, 4, 4, 4)
          vbox.set_spacing(2)
  
          msg_font = self.get_font('fixed', 12)
          tw = Widgets.TextArea(wrap=False, editable=False)
          tw.set_font(msg_font)
          tw.set_text(help_txt)
          vbox.add_widget(tw, stretch=1)
  
          btns = Widgets.HBox()
          btns.set_border_width(4)
          btns.set_spacing(3)
  
          def _close_cb(w):
              self.ds.remove_tab(tabname)
  
          btn = Widgets.Button("Close")
          btn.add_callback('activated', _close_cb)
          btns.add_widget(btn, stretch=0)
          btns.add_widget(Widgets.Label(''), stretch=1)
  
          vbox.add_widget(btns, stretch=0)
  
          self.ds.add_tab(wsname, vbox, group, tabname)
          self.ds.raise_tab(tabname)
docs: Show help text in a closeable tab window.  The title of the
          window is set from ``name`` prefixed with 'HELP:'