Python parameter with None | union type is logged as unknown

[calbach]

🐛 Bug

# template.ipynb parameters block
foo: None|str = None

$ papermill -p foo BAR ...
Passed unknown parameter: foo

Expected: this warning not to show up, foo should be recognized as a valid parameter.

Also note:

• Despite the warning, the above example still properly injects the parameter value
• Optional[str] does not suffer from this issue, just type union style
• str|None (change the type order) produces the same warning log

papermill version == 2.6.0