anchor.diff:      optionals
       optionalString
       platforms;
  +  inherit (pythonPackages)
  +    isPy3k;
   in
   
   let
     optionalPlugins = {
       # TODO: write a generic function to detect null dependencies
       acousticbrainz =
  -      if python2Packages.requests2 != null then
  +      if pythonPackages.requests2 != null then
           true
         else
           false;
  
positive.code:     flac
      imagemagick
      mp3val
      python2Packages.beautifulsoup
      python2Packages.discogs-client
      python2Packages.enum34
      python2Packages.flask
      python2Packages.itsdangerous
      python2Packages.jellyfish
      python2Packages.jinja2
      python2Packages.mock
      python2Packages.mpd
      python2Packages.munkres
      python2Packages.musicbrainzngs
      python2Packages.mutagen
      python2Packages.nose
      python2Packages.pathlib
      python2Packages.pyacoustid
      python2Packages.pyechonest
      python2Packages.pylast
      python2Packages.pyxdg
      python2Packages.pyyaml
      python2Packages.rarfile
      python2Packages.responses
      python2Packages.requests2
      python2Packages.unidecode
      python2Packages.werkzeug
    ] ++ optional enableAlternatives (
        import ./plugins/beets-alternatives.nix {
          inherit
            stdenv
            buildPythonPackage
            fetchFromGitHub
            python2Packages;
        }
      )
      /* FIXME: Causes other plugins to fail to load
  
negative.code:       else
          false;
      thumbnails =
        if pythonPackages.pyxdg != null then
          true
        else
          false;
      web =
        if pythonPackages.flask != null then
          true
        else
          false;
  