Setup an xmltextReader to parse a preparsed XML document.
           This reuses the existing @reader xmlTextReader.

def NewWalker(self, reader):
        """Setup an xmltextReader to parse a preparsed XML document.
           This reuses the existing @reader xmlTextReader. """
        if reader is None: reader__o = None
        else: reader__o = reader._o
        ret = libxml2mod.xmlReaderNewWalker(reader__o, self._o)
        return ret