Add node when taxonomy term is added

addNATNode.php

<?php
    /**
    *  This Drupal 7 helper function adds a node of bundle 'topic' which has a nat term reference
    *  field 'field_about' which should correspond to the parent term for this node's
    *  sibling 'node'. 
    */

    public function addNATNode($tid, $name) {
    $parent = db_query('SELECT parent FROM taxonomy_term_hierarchy WHERE tid = :tid', array(':tid' => $tid))->fetchField();
    $topic = entity_create('node', array('type' => 'topic'));
    $topic->uid = 1;
    $topic_wrapper = entity_metadata_wrapper('node', $topic);
    $topic_wrapper->title = $name;
    $topic_wrapper->title = $topic_wrapper->title->value();
    if ($parent > 0) {
      $topic_wrapper->field_about->set(array($parent));
    }
    $topic_wrapper->status = 1;
    $topic_wrapper->save();
    $node_id = $topic_wrapper->getIdentifier();
    $data = array(
      'nid' => $node_id,
      'tid' => $tid,
      'vid' => 49
    );
    switch (drupal_write_record('nat', $data)) {
      case FALSE:
        $message = "NAT record save failed\n";
        echo $message;
        $this->queueMessage($message, MigrationBase::MESSAGE_INFORMATIONAL);
        break;
      case SAVED_NEW:
        $message = "New NAT record saved for $name \n";
        echo $message;
        $this->queueMessage($message, MigrationBase::MESSAGE_INFORMATIONAL);
        break;
      case SAVED_UPDATED:
        $message = "NAT record updated for $name \n";
        echo $message;
        $this->queueMessage($message, MigrationBase::MESSAGE_INFORMATIONAL);
        break;
    }
  }