```suggestion      url = "https://maude.cs.illinois.edu/w/images/d/d3/Maude-${version}.tar.gz";      sha256 = "b112d7843f65217e3b5a9d40461698ef8dab7cbbe830af21216dfb924dc88a2f";    };      fullMaude = fetchurl {      url = "https://maude.cs.illinois.edu/w/images/0/0a/Full-Maude-${version}.zip";  ```