fromJson static method
Creates an instance of this class from the constructor parameters defined in the json
object.
Example
class Item extends Serializable {
  const(this.name, this.count);
  final String name;
  final int? count;
}
final Item x = Item.fromJson({ 
  'name': 'apple', 
  'count': 10,
});
Implementation
static Object fromJson(final dynamic json)
  => throw _unimplementedError('fromJson');