Set the value

def set(self, val):
        """Set the value"""
        import time
        now = time.time()
        expected_value = []
        new_val = {}
        new_val['timestamp'] = now
        if self._value != None:
            new_val['last_value'] = self._value
            expected_value = ['current_value', str(self._value)]
        new_val['current_value'] = val
        try:
            self.db.put_attributes(self.id, new_val, expected_value=expected_value)
            self.timestamp = new_val['timestamp']
        except SDBResponseError, e:
            if e.status == 409:
                raise ValueError, "Sequence out of sync"
            else:
                raise