variablesFromJson function
Implementation
List<Variable>? variablesFromJson(Map<String, dynamic>? json) {
if (json == null) return null;
final data = json.entries
.map((e) => Variable.fromJson((e.value as Map<String, dynamic>)
..putIfAbsent('variable_name', () => e.key)))
.toList();
return data;
}