code: def add_object(self, obj):
          '''add an object to a layer'''
          state = self.state
          if not obj.layer in state.layers:
              # its a new layer
              state.layers[obj.layer] = {}
          state.layers[obj.layer][obj.key] = obj
          state.need_redraw = True
          if (not self.legend_checkbox_menuitem_added and
              isinstance(obj, SlipFlightModeLegend)):
              self.add_legend_checkbox_menuitem()
              self.legend_checkbox_menuitem_added = True
              self.SetMenuBar(self.menu.wx_menu()f add_object(self, obj):
          '''add an object to a layer'''
          state = self.state
          if not obj.layer in state.layers:
              # its a new layer
              state.layers[obj.layer] = {}
          state.layers[obj.layer][obj.key] = obj
          state.need_redraw = True
          if (not self.legend_checkbox_menuitem_added and
              isinstance(obj, SlipFlightModeLegend)):
              self.add_legend_checkbox_menuitem()
              self.legend_checkbox_menuitem_added = True
              self.SetMenuBar(self.menu.wx_menu())
docs: add an object to a layer