Adding a colormap to a Layer or FeatureGroup

Hopefully, this is just a case of I'm-Doing-It-Wrong.

I'd like to be able to associate a colormap with a specific layer (e.g. GeoJson or TopoJson layer), independently of say, another layer of just markers or just a different choropleth layer. This way, if I deselect a layer in the LayerControl, both the GeoJson layer and the associated colormap go away (which also lets me have a separate colormap per Geo/TopoJson layer).

I've tried adding the colormap to the layer itself as well as adding both the layer and colormap to a FeatureGroup, but neither of these approaches seem to work.

Have a look at: https://github.com/eddies/folium/blob/59f88bca397a600b138abfc21591373ac3a66a78/tests/test_colormap_layer.py for an example (sorry, it's not a Jupyter notebook--long story about problems w/ Jupyter and virtualenvs)

从 tests/test_colormap_layer.py 开始，并运行现有示例，以了解 colormap 如何附加到 GeoJson、TopoJson 和 FeatureGroup 图层。完成的标准是：图层的 colormap 在 LayerControl 中跟随该图层，在取消选择图层时消失，同时不同图层可以分别保留各自的 colormap。