NaN columns to remove refactoring

[alessiamarcolini]

Why in https://github.com/HK3-Lab-Team/umapviz/blob/master/src/umapviz/umap_exp.py#L299 we are not using methods/properties of DataFrameWithInfo to get the columns to remove / to keep?

We could use least_nan_cols method (https://github.com/HK3-Lab-Team/pd_extras/blob/master/src/pd_extras/dataframe_with_info.py#L503) to not reimplement the calculation from scratch

[lorenz-gorini]

You are right. I may had forgotten about that method and that I created it for that purpose when I rewrote the code. :(

[alessiamarcolini]

No worries, let's write some tests before and then we can refactor it!