Tqz/utils refactor

[ztq1996]

Problem & Solution Description (including issue #)

Code Quality

• [ ] My code follows the code style of this project
• [ ] I have written unit tests or justified all instances of #pragma: no cover; in the case of a bugfix, a new test that breaks as a result of the bug has been added
• [ ] My code contains relevant comments and necessary documentation for future maintainers; the change is reflected in applicable demos/tutorials (with output cleared!) and added/updated docstrings use the NumPy docstring format
• [ ] Any breaking changes, described above, are accompanied by backwards compatibility and deprecation warnings

[hangqianjun]

Unit test seems to fail due related to TableHandle.write() called for path inprogress_PZflowPDF.pkl with no data. Tagging @jfcrenshaw here in case he knows more about it.

[jfcrenshaw]

I had a look at this, but I think it's more of an issue with stage finalization stuff. Maybe @eacharles can illuminate us? If it turns out it's a problem with PZFlow somehow, I'm happy to help fix.