I'm able to create line charts, profile graphs, etc. on a feature layer, but I have to use the CIMChart classes in the ArcGIS.Core.Internal.CIM namespace. I don't see any documentation online (yay IntelliSense), and the namespace implies that it isn't intended for "public" use. Are there any plans to move the charting API into a publicly documented namespace? If not, what is the best way to plan on creating charts in the future?