Hi,
Nice new contributor 
try something like this Add Ptr KNearest::load and python binding by LaurentBerger 路 Pull Request #14332 路 opencv/opencv 路 GitHub
" Merge with extra: add data for PR 14332 by LaurentBerger 路 Pull Request #597 路 opencv/opencv_extra 路 GitHub"
of course with your pr ref for opencv_extra
" Merge with extra :Added Darknet Tanh Test Data by aryanshomray 路 Pull Request #847 路 opencv/opencv_extra 路 GitHub"