// Grab the collection attribute key category
$eaku = AttributeKeyCategory::getByHandle('collection');
 
// Set the collection attribute key category to editable
$eaku->setAllowAttributeSets(AttributeKeyCategory::ASET_ALLOW_SINGLE);
 
// Add the "Locations" attribute set
$cas = $eaku->addSet('location',t('Locations'),$this->pkg, 0);
 
// Create the "Region" drop down
$cak = CollectionAttributeKey::getByHandle('regions');
if (!is_object($cak)) {
   $at = AttributeType::getByHandle('select');
   $cak = CollectionAttributeKey::add(
      $at, 
      array(
         'akHandle' => 'regions', 
         'akName' => t('Region'), 
         'akIsSearchable' => true, 
         'akIsSearchableIndexed' => true,
         'akSelectAllowMultipleValues' => true,
         'akSelectAllowOtherValues' => false,
         'akSelectOptionDisplayOrder' => 'display_asc',
      ), 
     $this->pkg
   )->setOptions(
      /* This should set the drop down options */
      array(
         'Eastern',
         'Northern',
         'Southern',
         'Western'
      )
   )
   ->setAttributeSet($cas);
}