Relationship to map variable

Suppose I have a class as follows:

@NodeEntity
public class Car{
  @Id
   String plateNumber;
    @Property
   String color;
}

@NodeEntity
public class Person {
 @Property
   String idCardNumber;

    Map <String, Car> cars;
}

How to define a relationship from the class Person and Car given the it's a map that is being used in the class Person ?