Attach html to feature group

I am looking to add an HTML legend at the bottom corner of each layer. The legend will be different per layer.

I can add an HTML legend to the base map using `map.get_root().html.add_child(<html>)`, however this will only display the same text for all layer. I am looking instead for a method to attach html to a feature group, ie, something like `feature_group.get_root().html.add_child(<html>)`.

