docs: def _SyncAttributes(self):
      """Sync the new attributes to the synced attribute cache.
  
      This maintains object validity.
      """
      # This effectively moves all the values from the new_attributes to the
      # synced_attributes caches.
      for attribute, value_array in iteritems(self.new_attributes):
        if not attribute.versioned or self.age_policy == NEWEST_TIME:
          # Store the latest version if there are multiple unsynced versions.
          value = value_array[-1]
          self.synced_attributes[attribute] = [
              LazyDecoder(decoded=value, age=value.age)
          ]
  
        else:
          synced_value_array = self.synced_attributes.setdefault(attribute, [])
          for value in value_array:
            synced_value_array.append(LazyDecoder(decoded=value, age=value.age))
  
          synced_value_array.sort(key=lambda x: x.age, reverse=True)
  
      self.new_attributes = {}
      self._to_delete.clear()
      self._dirty = False
      self._new_version = False