How to supply obj.setOwner()

I have trouble finding how or what I should supply obj.setOwner().

From some digging I found that obj.getOwner() returns a "PropertiedUser". Is that what I should supply the setOwner?
If so how do I make PropertiedUser out of a string?

https://docs.plone.org/develop/plone/content/ownership.html

I saw that page, but it doesn't say how to get the user object or member object from a string.
For example if I have the username is there method to return the PropertiedUser representation of that username?

Edit: Found it: https://docs.plone.org/develop/plone.api/docs/api/user.html

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