def METHOD_NAME(self, request, object_id, extra_context=None):
    """Allow selecting versions to compare."""
    opts = self.model._meta
    object_id = unquote(object_id)
    current = get_object_or_404(self.model, pk=object_id)
    # As done by reversion's history_view
    action_list = [
        {
            "revision": version.revision,
            "url": reverse("%s:%s_%s_compare" % (self.admin_site.name, opts.app_label, opts.model_name), args=(quote(version.object_id), version.id)),
        } for version in self._reversion_order_version_queryset(Version.objects.get_for_object_reference(
            self.model,
            object_id).select_related("revision__user"))]
    context = {"action_list": action_list,
               "opts": opts,
               "object_id": quote(object_id),
               "original": current,
              }
    extra_context = extra_context or {}
    context.update(extra_context)
    return render(request, self.compare_list_template or self._get_template_list("compare_list.html"),
                  context)