prepare_umap_data code duplication

[alessiamarcolini]

It seems there is a private method of UmapExperiment _prepare_umap_data who does the exact same things of the function prepare_umap_data in the umap_functions module, i.e. removing NaNs columns and train/test splitting.

Why code duplication? Which is the "most correct" one?

[lorenz-gorini]

UmapExperiment Is meant to be the correct way to do things and it should replace the functions from umap_functions.
They were both kept in place during transition (we should test if they both yield the same results)