@Entity
@NoSql(dataType="userGroup", dataFormat=DataFormatType.MAPPED)
public class Group extends JPAMongoBaseEntity {
	@Id
	@Field(name="_id")
	@GeneratedValue
	private String id;
	
	// Only the direct subGroup are set (not the subGroup of the subGroup)
	@OneToMany(targetEntity=Group.class, fetch=FetchType.LAZY, cascade=CascadeType.REMOVE)
	@Field(name="directSubGroups")
	private List<Group> directSubGroups = new ArrayList<>();
...