google-cloud-logging version: 1.8.0

I want to send structured logs to stackdriver from Python using the standard logging module. You can integrate structured logging to the Python logging module with either https://github.com/madzak/python-json-logger or http://www.structlog.org/en/stable/. Would be great to preserve those structures as part of jsonPayload when sent to stackdriver. Currently, these get stringified and sent as jsonPayload.message instead.