set method
Write a property value given an instance
instance the instance
value the value to write
context the context object
Implementation
@override
void set(dynamic instance,dynamic value, MappingContext context) {
var m = mapping ?? (mapping = mapper.getMappingX(sourceType, targetProperty.getType())); // TODO
targetProperty.set(instance, mapper.map(value, context: context, mapping: m), context); // recursive call!
}