title: How to get all users in one organization unit using Google Directory API
body: <p>In the new released Google Directory API,  I cannot find a method to get all users in a specific organization unit of Google Apps.  Is it possible? And how?   Based on the Google Directory API document, programmers can get all the organization  units, or all the users for the whole domain, but there is no description on how to get users of one organization unit.  This feature is crucial important to construct the organizations/users hierarchical tree.  Please help, thanks. </p>