## What changes were proposed in this pull request?
When we clean a closure, if its outermost parent is not a closure, we won't clone and clean it as cloning user's objects is dangerous. However, if it's a REPL line object, which may carry a lot of unnecessary references(like hadoop conf, spark conf, etc.), we should clean it as it's not a user object.
This PR improves the check for user's objects to exclude REPL line object.
## How was this patch tested?
existing tests.
Author: Wenchen Fan <wenchen@databricks.com>
Closes#12327 from cloud-fan/closure.
1d04c86fc5