Update distributed.py (#617)

# Pull Request

## What problem does this PR solve?

Issue Number: Fixed #

## Possible side effects?

- Performance:

- Backward compatibility:

Author: anakinxc

spu/utils/distributed.py

@@ -26,6 +26,7 @@
     SAMPLE_DEVICES_DEF,
     dtype_spu_to_np,
     shape_spu_to_np,
+    save,
 )