Add missing file from last commit

tensorpack/utils/compatible_serialize.py

+#!/usr/bin/env python
+
+import os
+from .serialize import loads_msgpack, loads_pyarrow, dumps_msgpack, dumps_pyarrow
+
+"""
+Serialization that has compatibility guarantee (therefore is safe to store to disk).
+"""
+
+__all__ = ['loads', 'dumps']
+
+
+# pyarrow has no compatibility guarantee
+# use msgpack for persistent serialization, unless explicitly set from envvar
+if os.environ.get('TENSORPACK_COMPATIBLE_SERIALIZE', 'msgpack') == 'msgpack':
+    loads = loads_msgpack
+    dumps = dumps_msgpack
+else:
+    loads = loads_pyarrow
+    dumps = dumps_pyarrow