Please help to complete this code

[Brap]

bpl.py class \[code\]'bpl_company_id': fields.function(_get_company_data, fnct_inv=_set_company_data, type='one2many', relation='hr.department', string="Company"),bpl_estate_idbpl_division_id\[/code\]i need to add below sql query and retrieve companies (no parent id)then need to get estate under that selected companythen division under selected estatecompany - > Estate -> Divisionmy incomplete function\[code\] cr.execute(""" select * from hr_department where parent_id is null """)return cr. fetch method..\[/code\]please advice me to complete this code.try with various samples.but unable to get the result