Hello Mohammed,

You just need to add the module as in dependency of your __openerp__.py file in which "hr.payslip" class is defined.  For example, hr.payslip is defined in hr_payroll module. So you need to add "hr_payroll" in "depends" key in your __openerp__.py file like as follows,

'depends': ["hr_payroll"]

Tips : When you inherit any model, you must need to add the module in which that model is defined as inside dependency in your module. 

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Regards

Odoo Police ["Justice for all !"]

Do you have depends hr.payslip in openerp.py? Maybe could solve this problem.