code: def set(self, val):
          
          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
docs: Set the value