from odoo import models, fields, api class Approver_PO(models.Model):

                _inherit = 'purchase.order'

    def get_user_id(self):

        return self.env.uid

    @api.multi

    def button_approve(self, force=False):

        self.write({'state': 'purchase'})

        self._create_picking()

        approver_id = fields.Many2one('res.users','Approved By', default=_get_user_id)

        if self.company_id.po_lock == 'lock':

            self.write({'state': 'done'})

        return {}