Tasks (near and far future):
1) Make sure that the fitting range for the BDT is OK in all categories (Huiling)
2) Check variable bins size in the BDT output score (ZhangYu)
3) Add geometrical average of b scores as input (Huiling)
4) Check what happens with the binning of the inputs (Huiling/ZhangYu?)
5) Check XGboost (ZhangYu)