What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

kind bug

What does this PR do / why do we need it:
In pynative mode, memory resource would not release after run op finish. It will cause memory not enough. This pr is used to fix it.

Which issue(s) this PR fixes:

Fixes #I1GOQH

Special notes for your reviewers: