Hii, I am trying to write a python expression in xml file for salary rule. My expression is multi line, so when I import and compute salary, it gives error on python expression...

Python code

unpaid = payslip.total_unpaid_leave_days 
basic = contract.wage 
result =  basic - (unpaid * basic/30)

xml code

<record id="hr_payroll.hr_rule_basic" model="hr.salary.rule">
            <field name="name">Basic Salary</field>
            <field name="sequence" eval="1"/>
            <field name="code">BASIC</field>
            <field name="category_id" ref="hr_payroll.BASIC"/>
            <field name="condition_select">none</field>
            <field name="amount_select">code</field>
            <field name="amount_python_compute">unpaid = payslip.total_unpaid_leave_days basic = contract.wage result =  basic - (unpaid * basic/30)</field>
 </record>

I put it in one line, it did not work...How to do it here