switched dangerous default arguments to None

[shayneofficer]

Per the code sniff here using mutable lists/dictionaries as default arguments is a bug risk.

[jace]

Hi, I was on holiday and missed this. I’m not sure why you’ve closed the PR. In any case, I’ve implemented similar fixes in #637.

[shayneofficer]

Hi @jace ! no worries, thanks for the response 😄 I closed it since one of the build pipeline checks said I introduced a new bug I think - happy to re-open if you think this change is valuable though!

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