odoo - get value from many2one field

My code:

class SaleOrder(osv.Model):
    _inherit = 'sale.order'

    _columns = {
        'xx_delivery_date': fields.date(string='Delivery date'),
        'xx_payment_method': fields.many2one('xx.payment.method',
                                             string='Payment method'),
        'xx_insurance_type': fields.many2one('xx.insurance.type', string='Insurance')
    }

    def _amount_insurance(self, cr, uid, val1, context=None):
        val = 0.0
        insurance_chosen = self.pool.get('xx.insurance.type').browse(cr, uid, insurance_percentage.id,context=context)
        val = val1*insurance_chosen/100
        return val

class InsuranceType(osv.Model):
    _name='xx.insurance.type'

    _columns = {
        'name' : fields.char(size=128, string = 'Name'),
        'sale_ids': fields.one2many('sale.order', 'xx_insurance_type', string = 'Sale orders'),
        'insurance_percentage' : fields.float('Insurance cost in %')
    }

I am trying to get the float from the 'insurance_percentage' field and add this percentage to val1.

At the moment my code results in

'Global name insurance_percentage not defined,

So I have to somehow tell the function to take the variable from the InsuranceType class but I don't know how to do this.

For many2one field, we need to first take id of that record and than browse that record with id and take desire value from that.

Try with this code:

def _amount_insurance(self, cr, uid, ids, val1, context=None):
    val = 0.0
    for insurance in self.browse(cr, uid, ids,context=context):
        if insurance.xx_insurance_type:
            val = (val1 * (insurance.xx_insurance_type.insurance_percentage/100))
    return val