useful with formblock to save the parent node to the created node's reference field

gistfile1.php

<?php
function HOOK_ugc_node_presave($node) {
  $journal_wrapper = entity_metadata_wrapper('node', $node);

  // If this is a new journal entry set it's parent reference.
  if ($journal_wrapper->getBundle() == 'journal_entry') {

    // If this is the first time the journal is saved, attach the course.
    if (!$journal_wrapper->getIdentifier() && arg(0) == 'node' && is_numeric(arg(1))) {
      $course_wrapper = entity_metadata_wrapper('node', arg(1));
      $journal_wrapper->field_course_reference->set(arg(1));
    }
  }
}

?>

What is $course_wrapper created for?