Since these transaction config items are only meant to be used by advanced (internal) integrators, we're not providing an API, which would invite questions about what these things are for.
The right way to do this will be to setup these parameters as custom_payload on the SimplaGraphStatement. I put a test in to make sure they're passed through.
I also split execute_graph into a sync and async version, so I'm putting it up for review.
+1 LGTM coverage is provided by additional tests, and async function is covered as it's used by our sync calls as well. I'm moving this to done.