putRelationship method
Implementation
@override
FutureOr<bool> putRelationship(
Object oId, Type valuesType, Iterable<Object> valuesIds) {
var typeRelationships =
_relationships.putIfAbsent(valuesType, () => <Object, Set<Object>>{});
typeRelationships[oId] = valuesIds.toSet();
return true;
}