anchor.diff:  
     pkg = self: stdenv.mkDerivation (attrs // {
       name = "${name}-${version}";
  -    inherit version src buildInputs;
  +    inherit version src;
   
       MIX_ENV = mixEnv;
       MIX_DEBUG = if enableDebugInfo then 1 else 0;
  
positive.code:       addToSearchPath ERL_LIBS "$1/lib/erlang/lib"
      '';
  
      nativeBuildInputs = [ elixir hex ];
      propagatedBuildInputs = propagatedBuildInputs ++ beamDeps;
  
      buildPhase = attrs.buildPhase or ''
  
negative.code: , version
  , src
  , buildInputs ? [ ]
  , nativeBuildInputs ? [ ]
  , beamDeps ? [ ]
  , propagatedBuildInputs ? [ ]
  , postPatch ? ""
  