tokens: Today , machine learning requires human capital to perform a variety of tasks including 1 ) composition and aggregation of machine learning " primitives " , e.g. , kernels of code that clean , decide , classify / label , cluster / organize , and rank the input dataset to produce an output ; 2 ) selection of ML models that have already been generated such as from OpenML , ModelZoo , UC Irvine ML repository , Kaggle , etc .