where should i build a function which run on click of my custom button on inherited hr.payslip model

xml:

<record id="hr_payslip_form" model="ir.ui.view">
    <field name="name">hr.payslip.form</field>
    <field name="model">hr.payslip</field>
    <field name="type">form</field>
    <field name="inherit_id" ref="hr_payroll.view_hr_payslip_form"/>
    <field name="arch" type="xml">
            <xpath expr="//header" position="inside">
                <button name="my_button" string="Print2" class="oe_highlight"/>
            </xpath>
    </field>
</record>

models.py

class custom_hr_payslip(models.Model):
    _name = 'custom.hr.payslip'
    _inherit = 'hr.payslip'

    @api.one
    def my_button(self):
        print("#########################################################")