https://haifengl.github.io/api/java/smile/regression/GradientTreeBoost.html
GradientTreeBoost
declaration: package: smile.regression, class: GradientTreeBoost
https://haifengl.github.io/api/java/smile/classification/GradientTreeBoost.TrainingStatus.html
GradientTreeBoost.TrainingStatus
declaration: package: smile.classification, class: GradientTreeBoost, record: TrainingStatus