def _ancestry_line(self):
        '''
        Returns the ancestry of this dict, back to the first dict that we don't
        recognize or that has more than one backer.
        '''
        b = self._get_backers()

        while len(b) == 1:
            yield b[0]
            if not hasattr(b[0], '_get_backers'):
                break
            b = b[0]._get_backers()
Returns the ancestry of this dict, back to the first dict that we don't
        recognize or that has more than one backer.