"shap" as a dependency?

[almostintuitive]

Hi! Fasttreeshap is great example of real applied computer science research, thank you! It is much faster and configurable than the original shappackage.
We were wondering if the referenced original shap package could be removed from Fasttreeshap, as it looks like it's only used for non-essential code, and as shap is a huge library, it could speed up the installation process and could make Fastreeshap's installation a lot more lightweight.

Thank you for considering it!