Multiclass Performance Evaluation Toolkit // Implementation of custom 'tidymodels' metrics for multi-class prediction models with a single negative class. Currently are implemented macro- average sensitivity and specificity as in Mortaz, Ebrahim (2020) "Imbalance accuracy metric for model selection in multi- class imbalance classification problems doi:10.1016/j.knosys.2020.106490 and a generalized weighted Youden index as in Li, D.L., Shen F., Yin Y., Peng J.X and Chen P.Y. (2013) Weighted Youden index and its two-independent- sample comparison based on weighted sensitivity and specificity doi:10.3760/cma.j.issn.0366-6999.20123102.