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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def readerWalker(self):
 """Create an xmltextReader for a preparsed document. """

        ret = libxml2mod.xmlReaderWalker(self._o)
        if ret is None:raise treeError('xmlReaderWalker() failed')
        __tmp = xmlTextReader(_obj=ret)
        return __tmp