shelve(writeback=true) danger...

[Matthew Wilson]

I'm going to use shelve to work with some large dicts, and I'm going to
use writeback=True to make sure all the edits get written back to the
file when I close it.  Is there a way to force a writeback without
closing?  It would be nice if I could occasionally flush the caches in
memory and write everything back to files without having to close and
reopen my shelf.