How to show the selected item object inside the form factory in Vaadin Flow?

Question

I am using the crud library of Aljandro, and Vaadin 21.0.3

When I select a user (transporter in my example) from the crud grid table, the details show successfully. But how can I get the selected transporter's object from inside the form itself, so I can show relations?

For example, if I have the transporter object inside the from factory, I would create a checkbox list to present the drivers [relationship is OneToMany]

Here is the code

        DefaultCrudFormFactory<Transporter> formFactory = new DefaultCrudFormFactory<>(Transporter.class) {
            @Override
            protected void configureForm(FormLayout formLayout, List<HasValueAndElement> fields) {
                Component nameField = (Component) fields.get(0);
                formLayout.setColspan(nameField, 2);
            }
        };
...

        formFactory.setFieldProvider("drivers",
                new CheckBoxGroupProvider<>("Drivers",
                        formFactory.getNewInstanceSupplier().get().getDrivers(),   <<<<<< How to get the selected Transporter object? 
                        Driver::getFullName));

Does anyone have an example of crud with relation?

or, How to show the selected transporter's object inside the form factory?