def __init__(self, entity_or_blob_key, _values=None):
    """Constructor for wrapping blobstore entity.

    The constructor should not be used outside this package and tests.

    Args:
      entity: Datastore entity that represents the blob reference.
    """
    if isinstance(entity_or_blob_key, datastore.Entity):
      self.__entity = entity_or_blob_key
      self.__key = BlobKey(entity_or_blob_key.key().name())
    elif isinstance(entity_or_blob_key, BlobKey):
      self.__entity = _values
      self.__key = entity_or_blob_key
    else:
      TypeError('Must provide Entity or BlobKey')
Constructor for wrapping blobstore entity.

    The constructor should not be used outside this package and tests.

    Args:
      entity: Datastore entity that represents the blob reference.
    
mapreduce/lib/blobstore/blobstore.py