def __get_value(self, name):
    """Get a BlobInfo value, loading entity if necessary.

    This method allows lazy loading of the underlying datastore entity.  It
    should never be invoked directly.

    Args:
      name: Name of property to get value for.

    Returns:
      Value of BlobInfo property from entity.
    """
    if self.__entity is None:
      self.__entity = datastore.Get(
          datastore_types.Key.from_path(
              self.kind(), str(self.__key), namespace=''))
    try:
      return self.__entity[name]
    except KeyError:
      raise AttributeError(name)
Get a BlobInfo value, loading entity if necessary.

    This method allows lazy loading of the underlying datastore entity.  It
    should never be invoked directly.

    Args:
      name: Name of property to get value for.

    Returns:
      Value of BlobInfo property from entity.
    
mapreduce/lib/blobstore/blobstore.py