FigureWidget `shapes` property is empty, even when it's populated in `_props`

When using FigureWidget, the shapes property does not update properly.

Here is an example:

fig = go.Figure()
fig.update_layout(
    modebar={"add": ["drawline", "drawclosedpath", "eraseshape"]},
)
widget = go.FigureWidget(fig)
widget.show()

When I draw a shape, widget.layout["shapes"] remains empty. On the other hand, widget.layout._props["shapes"] is populated correctly.

This is using Plotly 6.2.0.

使用所示的 FigureWidget 示例重现问题，然后跟踪绘制形状后 widget.layout["shapes"] 和 widget.layout._props["shapes"] 是如何填充的。比较公共属性和内部 props 的行为，并确认公共 shapes 属性反映出所绘制的形状后即可完成。