How to mutate data on form submit of Relation Manager?

class TestRelationManager extends RelationManager
{
    use InteractsWithForms;    
    public ?array $data = [];
    protected static string $relationship = 'test';

    public function mount(): void
    {
        $this->form->fill();
    }

    public function form(Form $form): Form
    {
        return $form
            ->schema([
                // ...

            ])->columns(3)->statePath('data');
    }

    public function create(): void
    {
        dd($this->form->getState());
    }

    public function table(Table $table): Table
    {
        return $table
            // ...
    }
}

class TestRelationManager extends RelationManager
{
    use InteractsWithForms;    
    public ?array $data = [];
    protected static string $relationship = 'test';

    public function mount(): void
    {
        $this->form->fill();
    }

    public function form(Form $form): Form
    {
        return $form
            ->schema([
                // ...

            ])->columns(3)->statePath('data');
    }

    public function create(): void
    {
        dd($this->form->getState());
    }

    public function table(Table $table): Table
    {
        return $table
            // ...
    }
}