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I haven't come across such a function.
The way to get the information from the database would be to query the xoops_group_permission table to get the groups that have the module_admin right for that particular module, and then query the xoops_groups_users_link table to get the users in those groups.
Publicly displaying the usernames of admins is not necessarily a good idea from a security viewpoint, but that's up to you.