code: def hover(self, node):
          
          
          
          if self.popup == False: return
          if self.popup == True or self.popup.node != node:
              if self.popup_text.has_key(node.id):
                  texts = self.popup_text[node.id]
              else:
                  texts = None
              self.popup = popup(self._ctx, node, texts)
          self.popup.draw()
docs: Displays a popup when hovering over a node.