Personalizations passed as dictionaries cause AssertionErrors

[alichass]

Not sure if this is only happening on python 3.10 and above, but the culprit seems to be the type check on line 444 in mail.py: type(personalization) == Dict seems to evaluate to false even when the personalization instances.
I believe replacing the check with isinstance(personalization, Dict) should do the trick and leave things backwards compatible.
(maybe its worth doing this for line 447 as well?)

Let me know if it would be helpful for me to make the changes and create a PR.
Thanks!

[sklarsa]

Thank you for tracking this down! A PR would be fantastic if you have time

[sklarsa]

closed by #114