anchor.diff:  
     buildInputs = with pythonPackages; [
       beautifulsoup4
  -    flask
  +    imagemagick
       mock
       nose
  -    pyechonest
  -    pylast
       rarfile
  -    requests2
       responses
     ];
   
  
positive.code: 
  in buildPythonPackage rec {
    name = "beets-${version}";
    version = "1.3.11";
    namePrefix = "";
  
    src = fetchFromGitHub {
      owner = "sampsyo";
      repo = "beets";
      rev = "v${version}";
      sha256 = "16jb1frds9vl40n9hy18x9xipxfzln3ym823vx8jymhv3by8p62m";
    };
  
    propagatedBuildInputs = [
      pythonPackages.enum34
      pythonPackages.munkres
      pythonPackages.musicbrainzngs
      pythonPackages.mutagen
  
negative.code:     "bench" "bpd" "bpm" "bucket" "convert" "cue" "duplicates" "embedart"
      "filefilter" "freedesktop" "fromfilename" "ftintitle" "fuzzy" "ihate"
      "importadded" "importfeeds" "info" "inline" "keyfinder" "lyrics"
      "mbcollection" "mbsync" "metasync" "missing" "permissions" "play"
      "plexupdate" "random" "rewrite" "scrub" "smartplaylist" "spotify" "the"
      "types" "zero"
    ];
  
    enabledOptionalPlugins = attrNames (filterAttrs (_: id) optionalPlugins);
  