anchor.diff:    optionalPlugins = {
       absubmit = enableAbsubmit;
       acousticbrainz = enableAcousticbrainz;
  +    aura = enableAura;
       badfiles = enableBadfiles;
       beatport = enableBeatport;
       bpsync = enableBpsync;
  
positive.code: , enableAbsubmit         ? lib.elem stdenv.hostPlatform.system essentia-extractor.meta.platforms, essentia-extractor
  , enableAcousticbrainz   ? true
  , enableAcoustid         ? true
  , enableBadfiles         ? true, flac, mp3val
  , enableBeatport         ? true
  , enableBpsync           ? true
  
negative.code:   # unstable does not require bs1770gain[2].
    # [1]: https://discourse.beets.io/t/forming-a-beets-core-team/639
    # [2]: https://github.com/NixOS/nixpkgs/pull/90504
    version = "unstable-2021-03-08";
  
    src = fetchFromGitHub {
      owner = "beetbox";
      repo = "beets";
      rev = "debd382837ef1d30574c2234710d536bb299f979";
      sha256 = "sha256-I6ejW3f72fdzWoz7g4n8pDYz2NiHGrorLegUQhQOSiI=";
    };
  
    propagatedBuildInputs = [
  