letAsJMapOrNull function
Let's you cast input to a Map<String, dynamic> type if possible, or
returns null if the cast cannot be performed.
Implementation
Map<String, dynamic>? letAsJMapOrNull(dynamic input) {
return letAsOrNull<Map>(input)?.map((k, v) {
return MapEntry(letAsOrNull<String>(k), v);
}).nonNulls;
}