/**
  * @see AbstractObject::models
  */
 protected function modelsMagicProperty($function, $value)
 {
     switch ($function) {
         case 'get':
             $models = array();
             $rels_models = $this->relationships->get(FEDORA_MODEL_URI, 'hasModel');
             foreach ($rels_models as $model) {
                 $models[] = $model['object']['value'];
             }
             if (!in_array('fedora-system:FedoraObject-3.0', $models)) {
                 $models[] = 'fedora-system:FedoraObject-3.0';
             }
             return $models;
             break;
         case 'isset':
             $rels_models = $this->relationships->get(FEDORA_MODEL_URI, 'hasModel');
             return count($rels_models) > 0;
             break;
         case 'set':
             if (!is_array($value)) {
                 $models = array($value);
             } else {
                 $models = $value;
             }
             if (!in_array('fedora-system:FedoraObject-3.0', $models)) {
                 $models[] = 'fedora-system:FedoraObject-3.0';
             }
             foreach ($models as $model) {
                 if (!in_array($model, $this->models)) {
                     $this->relationships->add(FEDORA_MODEL_URI, 'hasModel', $model);
                 }
             }
             break;
         case 'unset':
             $this->relationships->remove(FEDORA_MODEL_URI, 'hasModel');
             break;
     }
 }
$password = '******';
// set up connection and repository variables
$connection = new RepositoryConnection($url, $username, $password);
$api = new FedoraApi($connection);
$repository = new FedoraRepository($api, new SimpleCache());
// try to fetch PID from repo
try {
    // drush_print("Attempting to access $objectPID from repository");
    $object = $repository->getObject($objectPID);
} catch (Exception $e) {
    drush_print("\n\n**********#######  ERROR  #######**********");
    drush_print("***Could not get object {$objectPID} from repo***\n\n");
    return;
}
drush_print("*************Object relationships before changes*************");
$object_content_models = $object->relationships->get('info:fedora/fedora-system:def/model#', 'hasModel');
print_r($object_content_models);
/** 
 * THIS IS FOR CHANGING PDF MODEL -> THESIS MODEL
 * 
 * Change the third argument to the 'add' and 'remove' methods to reflect the changes you need
**/
$fedrelsext = new FedoraRelsExt($object);
// add this relationship to all objects in the Research Collection
$fedrelsext->add("info:fedora/fedora-system:def/model#", "hasModel", "ir:thesisCModel");
// delete this relationship from all objects in the Research Collection
$fedrelsext->remove("info:fedora/fedora-system:def/model#", "hasModel", "islandora:sp_pdf");
drush_print("*************Object relationships AFTER changes*************");
$object_content_models = $object->relationships->get('info:fedora/fedora-system:def/model#', 'hasModel');
print_r($object_content_models);
drush_print("\nAll operations complete\n");