Comment 6 for bug 187449

As Ted Gould suggests it, a way of doing it should be to copy attributes which use a custom namespace

standart namespaces are:
u'sodipodi' :u'http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd',
u'cc' :u'http://web.resource.org/cc/',
u'svg' :u'http://www.w3.org/2000/svg',
u'dc' :u'http://purl.org/dc/elements/1.1/',
u'rdf' :u'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
u'inkscape' :u'http://www.inkscape.org/namespaces/inkscape',
u'xlink' :u'http://www.w3.org/1999/xlink',
u'xml' :u'http://www.w3.org/XML/1998/namespace'