Validation error to display issue keys

[Aleksei Kozlov]

I've made a validator that prevents users from closing Strategic Initiative issues until all of their initiatives are closed. I'm looking for a way to give user a list of resolved issues that have to be completed in an error message of the validator that uses scriptrunner portfolioChilderOf function:
Script JQL Functions (adaptavist.com)

I've seen a similar post already:
Solved: Validation error to display issue keys (atlassian.com)
But my JQL query includes use of issueFunction and I can't seem to manage it to run.

My JQL that returns a list of unresolved initiatives inside of strategic initiatives:
issueFunction in portfolioChildrenOf("issuekey = %{issue.key}") and issuetype = Initiative and resolution is EMPTY
I'm kind of confused with all of the ' and " used in it.
Is this even possible to use that issueFunction here?