'Return a new ``<Override>`` element with attributes set to parameter
values.'

@staticmethod
def new(partname, content_type):

    xml = (u'<Override    xmlns="%s"/>' % nsmap[u'ct'])
    override = parse_xml(xml)
    override.set(u'PartName', partname)
    override.set(u'ContentType', content_type)
    return override
