some `ElementFeature` convenience functions

[rkurchin]

• [ ] pull all possible values (categorical) or range (continuous) of encodable values
• [ ] dispatch encoding to elemental symbols (could be nice for demos)

[thazhemadam]

pull all possible values (categorical) or range (continuous) of encodable values

Without actually creating an ElementFeatureDescriptor object?

[rkurchin]

no, as a function with the EFD as an input (one thing I eventually want to play with is direct numerical encoding (as opposed to one-hot bins) and for that we'll need to be able to do things like normalize values for model input)

[thazhemadam]

If having different encoding schemes for an ElementFeatureDescriptor object is an idea, should we also consider bringing back encode_f and decode_f fields?

[rkurchin]

Yeah, I guess we might need to do that, since otherwise a lot of the fields (nbins, logspaced, etc.) would become irrelevant...so maybe the encoding functions would just get automatically built via arguments to the constructor that specify the encoding?

[rkurchin]

there is appeal to always having them attached in terms of dispatching the encoding on just the abstract FD type rather than having to define it for each subtype