def get_parent_id(org_client, account_id):
    """
    Query deployed AWS organanization for 'account_id. Return the 'Id' of
    the parent OrganizationalUnit or 'None'.
    """
    parents = org_client.list_parents(ChildId=account_id)['Parents']
    try:
        len(parents) == 1
        return parents[0]['Id']
    except:
        raise RuntimeError("API Error: account '%s' has more than one parent: "
                % (account_id, parents))