def write_configuration(self, out, secret_attrs=False):
        """Type-specific configuration for backward compatibility"""
        key_order = ['repo_nexml2json',
                     'number_of_shards',
                     'initialization', ]
        cd = self.get_configuration_dict(secret_attrs=secret_attrs)
        for k in key_order:
            if k in cd:
                out.write('  {} = {}'.format(k, cd[k]))
        for n, shard in enumerate(self._shards):
            out.write('Shard {}:\n'.format(n))
            shard.write_configuration(out)