Appends an address to the Abook addressbook
        vcard -- vCard to append
        filename -- unused
        return the new UID of the appended vcard

def append_vobject(self, vcard, filename=None):
        """Appends an address to the Abook addressbook
        vcard -- vCard to append
        filename -- unused
        return the new UID of the appended vcard
        """
        book = ConfigParser(default_section='format')
        with self._lock:
            book.read(self._filename)
            section = str(max([-1] + [int(k) for k in book.sections()]) + 1)
            Abook.to_abook(vcard, section, book, self._filename)
            with open(self._filename, 'w') as fp:
                book.write(fp, False)

        return Abook._gen_uid(book[section])