def _locked_json_write(self, data):
        assert self._thread_lock.locked()
        if self._read_only:
            return
        self._file.file_handle().seek(0)
        json.dump(data, self._file.file_handle(),
                  sort_keys=True, indent=2, separators=(',', ': '))
        self._file.file_handle().truncate()
Creates 2 mock buckets, each containing 4 objects, including 1 nested.
dataset/ETHPy150Open google/oauth2client/oauth2client/contrib/multistore_file.py/_MultiStore._locked_json_write--crossover with--dataset/ETHPy150Open GoogleCloudPlatform/gsutil/gslib/tests/test_wildcard_iterator.py/CloudWildcardIteratorTests.setUp