mplist_key -

       Copyright (C) 2001 Information-technology Promotion Agency (IPA)
       Copyright (C) 2001-2011 National Institute of Advanced Industrial Science and Technology (AIST)
       Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free
       Documentation License <http://www.gnu.org/licenses/fdl.html>.

Version 1.8.4                                    Mon Sep 25 2023                               mplist_key(3m17n)

       Return the key of the first property in a property list. The mplist_key() function returns the key of the
       first property in property list plist. If the length of plist is zero, it returns Mnil.

       mplist_key -

       MSymbol mplist_key (MPlist * plist)