class Brand(models.Model):
    _name = 'product_application.brand'

    name = fields.Char()
    models_ids = fields.One2many('product_application.model', 'brand_id', string="Models")


class Model(models.Model):
    _name = 'product_application.model'

    name = fields.Char()
    brand_id = fields.Many2one('product_application.brand', string="Brand")
    versions_ids = fields.One2many('product_application.version', 'model_id', string="Versions")


class Version(models.Model):
    _name='product_application.version'

    name = fields.Char()
    model_id = fields.Many2one('product_application.model',string="Model")