anchor.diff:  , tqdm
   # Advanced image processing (triples size of output)
   , advancedProcessing ? false
  -, opencv ? null
  +, opencv3 ? null
   , scikitimage ? null
   , scikitlearn ? null
   , scipy ? null
  
positive.code: }:
  
  assert advancedProcessing -> (
    opencv != null && scikitimage != null && scikitlearn != null
    && scipy != null && matplotlib != null && youtube-dl != null);
  
  buildPythonPackage rec {
  
negative.code:   propagatedBuildInputs = [
      numpy decorator imageio imageio-ffmpeg tqdm requests proglog
    ] ++ (stdenv.lib.optionals advancedProcessing [
      opencv3 scikitimage scikitlearn scipy matplotlib youtube-dl
    ]);
  
    meta = with stdenv.lib; {
  