anchor.diff:  
     src = fetchurl {
       url = "https://updates.signal.org/desktop/apt/pool/main/s/signal-desktop/signal-desktop_${version}_amd64.deb";
  -    sha256 = "17hxg61m9kk1kph6ifqy6507kzx5hi6yafr2mj8n0a6c39vc8f9g";
  +    sha256 = "1cirnnxy63jfkl98472k25bn1yp5apa7b5s74r42sxhlwzwkplw1";
     };
   
     nativeBuildInputs = [
  
positive.code:       else "");
  in stdenv.mkDerivation rec {
    pname = "signal-desktop";
    version = "5.0.0"; # Please backport all updates to the stable channel.
    # All releases have a limited lifetime and "expire" 90 days after the release.
    # When releases "expire" the application becomes unusable until an update is
    # applied. The expiration date for the current release can be extracted with:
  
negative.code:     pango
      systemd
      xorg.libxcb
      xorg.libxshmfence
    ];
  
    runtimeDependencies = [
  