Fatal error: Class 'DrupalNodeMigration' not found in migrate_d2d/d7/node.inc on line 10

I am trying to extend migrate_d2d module in D7 to migrate. I have wrote in node.inc

<?php

  abstract class AnatomyprepNodeMigration extends DrupalNode7Migration {
  public function __construct(array $arguments) {
    parent::__construct($arguments);
  }
}

By doing this, i have got following error. Fatal error: Class 'DrupalNodeMigration' not found. while re-registering migration classes.