popsu-d7/sites/all/modules/migrate/migrate_example/migrate_example.module

<?php

/*
 * You must implement hook_migrate_api(), setting the API level to 2, for
 * your migration classes to be recognized by the Migrate module.
 */
function migrate_example_migrate_api() {
  $api = array(
    'api' => 2,
  );
  return $api;
}