Feature-request: Allow identification with nodes of custom class label

[Croydon-Brixton]

Feature: Just noticed this now. It'd be useful to also allow identifying nodes with other (custom) classes where we determine the class-to-class mapping. I will add this as an extra small feature.

Originally posted by @Croydon-Brixton in https://github.com/ai4er-cdt/gtc-biodiversity/pull/28#discussion_r585391762