There is no  "volume-get-ltr" call in 7-Mode ontapi 
 
this is what i used a while back... while i muck around with 7-mode system.
 
    #Collecting 7Mode Volume Information and Storing in Perl %volinfo:
    my $outv = $ss->invoke( "volume-list-info" );
    if ($outv->results_status() eq "failed"){
        print ((caller(0))[3], $filer, $outv->results_reason(), "\n");
    } else {
        my $volume_info = $outv->child_get("volumes");
        my @result = $volume_info->children_get();
        foreach my $vol (@result){
            my $volname                                 = $vol->child_get_string("name");
            my $volid                                   = join (":", $filer, $volname);
            $volinfo{$volid}{'volid'}                   = $volid;
            $volinfo{$volid}{'uuid'}                    = $vol->child_get_string("uuid");
            $volinfo{$volid}{'name'}                    = $vol->child_get_string("name");
            $volinfo{$volid}{'state'}                   = $vol->child_get_string("state");
            $volinfo{$volid}{'type'}                    = $vol->child_get_string("type");
            $volinfo{$volid}{'sizeTotal'}               = $vol->child_get_int("size-total");
            $volinfo{$volid}{'sizeUsed'}                = $vol->child_get_int("size-used");
            $volinfo{$volid}{'sizeAvailable'}           = $vol->child_get_int("size-available");
            $volinfo{$volid}{'percentageUsed'}          = $vol->child_get_int("percentage-used");
            $volinfo{$volid}{'filesTotal'}              = $vol->child_get_int("files-total");
            $volinfo{$volid}{'filesUsed'}               = $vol->child_get_int("files-used");
            $volinfo{$volid}{'containingAggr'}          = $vol->child_get_string("containing-aggregate");
            $volinfo{$volid}{'filer'}                   = $filer;
        }
    }Yes, back in days.. i was using Perl..  😛