normalize static method
Normalize a key into a stable string representation
Implementation
static String normalize(Object? key) {
if (key == null) return 'null';
if (key is String) return key;
if (key is List) {
return '[${key.map((e) {
if (e is String) return "'$e'";
if (e is List) return normalize(e);
return e.toString();
}).join(', ')}]';
}
// For other objects, rely on toString()
// Users should override toString() for custom key objects
return key.toString();
}