def network_xml(identifier, xml, address=None):
    """Fills the XML file with the required fields.

     * name
     * uuid
     * bridge
     * ip
     ** dhcp

    """
    netname = identifier[:8]
    network = etree.fromstring(xml)

    subelement(network, './/name', 'name', identifier)
    subelement(network, './/uuid', 'uuid', identifier)
    subelement(network, './/bridge', 'bridge', None, name='virbr-%s' % netname)

    if address is not None:
        set_address(network, address)

    return etree.tostring(network).decode('utf-8')
Fills the XML file with the required fields.

     * name
     * uuid
     * bridge
     * ip
     ** dhcp