Select2("container") and drag/drop

Is this a bug?
#1

hi, i upgraded from 3.5 and i have issues with this code:

$(".select2_groups_sort").select2("container").find("ul.select2-choices").sortable({
  containment: 'parent',
  start: function() { $(".select2_groups_sort").select2("onSortStart"); },
  update: function() { $(".select2_groups_sort").select2("onSortEnd"); }
});

i get undefined for $(".select2_groups_sort").select2(“container”)
the old documentation show a similiar code to mine:
https://select2.github.io/select2/
What can i do?
Thanks

#2

Ok i read the file select2.full.js and there is NO reference to “container” or “onSortStart/end”…
Is not implemented anymore in this version of the library?