This procedure is defined in the server but not documented via ad_proc or proc_doc and may be intended as a private interface.
The procedure is defined as:
proc ::xotcl::checkoption_internal_to_xotcl1 {checkoptions} { set options [list] foreach option $checkoptions { if {$option eq "object-invar"} { lappend options "invar" } elseif {$option eq "class-invar"} { lappend options "instinvar" } else { lappend options $option } } return $options }