odoo-event-addons/event_question_sale/models/event_question.py

from odoo import api, fields, models, _


class EventQuestion(models.Model):
    _inherit = "event.question"

    add_products = fields.Boolean(
        string="Add extra products on answers",
        help="Checking this box allows",
    )
    qty_by_attendees = fields.Boolean(
        string="Multiply quantity by attendees count",
        help="For the questions asked only once per registration.\n"
        "If checked, Odoo will add the extra product for each attendee.\n"
        "Otherwise, Odoo will add the extra product only once.",
    )

    @api.onchange("question_type")
    def onchange_qtype(self):
        if self.question_type != "simple_choice" and self.add_product:
            self.add_product = False

    @api.onchange("once_per_order")
    def onchange_qtype(self):
        if not self.once_per_order and self.qty_by_attendees:
            self.qty_by_attendees = False