Explicitly decref py::object in PythonRpcHandler (#38366)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/38366
Test Plan: Imported from OSS
Differential Revision: D21537612
Pulled By: mrshenli
fbshipit-source-id: 089bcc3d7de3bce6e769f72d67e0e0f91e0219c6
