Odoo v12
On "create" method i just save records in self.order_line_copy, then in the method "_onchange_order_line"
i want to call wizard if self.order_line_copy not set, but i can't. 
Can you explain what the problem might be?
 
@api.model
def create(self, vals):
    ids = None
    res = super(VerificationPurchaseOrder, self).create(vals)
    if 'order_line' in vals.keys():
        for value in vals['order_line']:
            ids = value[2]
        if ids:
            records = self.env['purchase.order.line'].browse(ids)
            if records:
                self.order_line_copy = records
                for record in records:
                    try:
                        if 'check_status' in vals.keys():
                            if int(record.check_status) < int(vals['check_status']):
                                record.check_status = vals['check_status']
                    except ValueError:
                        _logger.info('Create method error: Cannot implicitly convert type \'string\' to \'int\'')
    return res


@api.onchange('order_line')
def _onchange_order_line(self):
    if not self.order_line_copy:
        form_view = self.env.ref('verification_purchase_order.user_error_wizard_form_view')
        return {
            'view_type': 'form',
            'view_mode': 'form',
            'res_model': 'user.error.wizard',
            'views': [
                (form_view.id, 'form'),
            ],
            'type': 'ir.actions.act_window',
            'target': 'new',
            'context': {
                'default_error_message': "Message.",
            },
        }