chooseone requires >1 proposition.
rankall/some require >2 propositions.

---- method : d-rules ----

{
chooseone' : ['plurality', 'majority', '25p','33p','66p',
                      'unan', //Unanimous
                      'unan-1' //Unanimous minus 1
           ],
'rankall' : [
'instrun', //Instant runoff
'borda' //Borda count
           ],

       'ranksome' : ['instrun','borda']  //<<same as for rankall>>
}