code: def get_object(self, name, master=None):
          
          widget = None
          if name in self.objects:
              widget = self.objects[name].widget
          else:
              xpath = ".//object[@id='{0}']".format(name)
              node = self.tree.find(xpath)
              if node is not None:
                  root = BuilderObject(self, dict())
                  root.widget = master
                  bobject = self._realize(root, node)
                  widget = bobject.widget
          if widget is None:
              msg = 'Widget "{0}" not defined.'.format(name)
              raise Exception(msg)
          return widget
docs: Find and create the widget named name.
          Use master as parent. If widget was already created, return
          that instance.