'Provide the datafile metadata for a previously opened object as a
dictionary. This is metadata that was included when the object was
first PUT, and does not include metadata set by any subsequent POST.
:returns: object\'s datafile metadata dictionary
:raises DiskFileNotOpen: if the
:func:`swift.obj.diskfile.DiskFile.open` method was not previously
invoked'

def get_datafile_metadata(self):

    if (self._datafile_metadata is None):
        raise DiskFileNotOpen()
    return self._datafile_metadata
