gpgme: how to check a key for source of wkd?

[Ludwig Reiter]

Hello!

I have read the AutomaticEncryption wiki page 
(https://wiki.gnupg.org/AutomatedEncryption).
To check for level 2 I need to know, if a key has a "wkd" source, but
a key in gpgme hasn't a source attribute.

How can I check with gpgme, that a key has a "wkd" source?

Kind Regards,
Ludwig

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