rendering a custom sublist

I have a custom record, which has a field (with id custrecord_ntnx_asset_tran_num) set as 'record is parent', so that it appears as a sublist on a sales order.

i would like to be able to render the sales order, and fields in the sublist on a suitlet. The role i'm using has view access to the sales order, and the custom record.

the code i have is something like this, based on KB article 65795   (https://netsuite.custhelp.com/app/answers/detail/a_id/65795)

var soRec = record.load({type:'salesorder', id: soId });

var sublistCount = soRec.getLineCount({sublistId: 'recmachcustrecord_ntnx_asset_tran_num'});