Search in the Variable array of the context for the given
           variable value.

def xpathVariableLookupNS(self, name, ns_uri):
        """Search in the Variable array of the context for the given
           variable value. """
        ret = libxml2mod.xmlXPathVariableLookupNS(self._o, name, ns_uri)
        if ret is None:raise xpathError('xmlXPathVariableLookupNS() failed')
        return xpathObjectRet(ret)