modificado3

    @api.depends('create_date')
    def _hora_boliviana(self):
        for record in self:
            hora_actual = (datetime.strptime(record.create_date,'%Y-%m-%d %H:%M:%S') - timedelta(hours = 4)).time().strftime('%H:%M:%S')
            record.hora_boliviana = hora_actual

hora_boliviana = fields.Text(compute='_hora_boliviana', store=True)