I have a model, ProgramClass, for which I'd like to be able use the CSV import functionality to load data. I am able to do so, BUT what happens is any relations (ie. has_one) are duplicated. Here is the model:

<?php
class ProgramClass extends DataObject {

  static $singular_name = "Scheduled Class";

  static $plural_name = "Scheduled Classes";

  static $db = array(
    'InviteOnly' => 'Boolean',
    'AgeYoungestYear' => 'Int',
    'AgeYoungestMonth' => 'Int',
    'AgeOldestYear' => 'Int',
    'AgeOldestMonth' => 'Int',
    'StartingTime' => 'Time',
    'EndingTime' => 'Time',
    'NumberOfClasses' => 'Int',
    'Days' => 'MultiEnum(array("Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"))',
    'Price' => 'Currency'
  );

  static $has_one = array(
    'Level' => 'Level',
    'Session' => 'ProgramSession',
    'Program' => 'Program'
  );
}

When I use the CSV import function as visible below in the bottom left corner:

It seems to work, except that it create duplicates of the Program DataObject, as you can see here:

There should only be one instance each of Mighty Mights and Advanced TRAC. My question is, how do I use CSV import without duplicating relations?

For reference here is the spreadsheet I'm using to export CSVs https://docs.google.com/spreadsheets/d/1Qn6nNHmkQFfNm1Y-CQhTI2-fDiN-rFqeJlv8WSmbDTs/edit?usp=sharing

Many thanks :)
Justin

P.S. - I should also mention I've attempted to extend CsvBulkLoader for ProgramClass, as demonstrated in the Silverstripe Developer Guides, but with no luck.