parentField property
getter/setter pair
If source is a List, parentField is the index of the inbound
reference. If source is a record, parentField is the field name of the
inbound reference. If source is an instance of any other kind,
parentField is the field containing the inbound reference.
Note: In v5.0 of the spec, @Field will no longer be a part of this
property's type, i.e. the type will become string|int.
parentField can be one of FieldRef, String or int.
Implementation
@optional
dynamic parentField;