ric accordingly the model evaluation and selection techniques we have described so far are the most important tools in data scientist' toolbox grid search and cross-validation as we've described them in this can only be applied to single supervised model we have seen beforehoweverthat many models require preprocessingand that in some applicationslike the face recognition example in extracting different representation of the data can be useful in the next we will introduce the pipeline classwhich allows us to use grid search and cross-validation on these complex chains of algorithms summary and outlook