StringMap!double map; assert(map.keys == []); map["c"] = 4.0; assert(map.keys == ["c"]); map["a"] = 3.0; assert(map.keys == ["c", "a"]); map.remove("c"); assert(map.keys == ["a"]); map.remove("a"); assert(map.keys == []); map["c"] = 4.0; assert(map.keys == ["c"]);