dynamic sig based off imap folder

[void]

Hi,

I have various mailing list emails filtered on the server
by the mail provider going into various imap folders, based
on various properties of the email, like List-Id: for example.

What I'd like to have within mutt is for it to dynamically
decide which signature file to use based on what imap
folder the mail being replied to is in.

In the .muttrc there's for example a line like this:

mailboxes =mutt-users =test

In the manual, the nearest thing I can find to do what
I'm describing is in "Example 3.8. Using MuttLisp expressions"
but I'm unsure what expressions to use for an imap folder,
how to test to see if mutt is in it.

thanks in advance for any assistance/pointers
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