Transform the supplied XML using the transform identified by key
        @param key: name of the transform to apply
        @param xml: XML to transform
        @param kwargs: XSLT parameters
        @return: Transform output or None if transform failed

def transform(self, key, xml, **kwargs):
        """
        Transform the supplied XML using the transform identified by key
        @param key: name of the transform to apply
        @param xml: XML to transform
        @param kwargs: XSLT parameters
        @return: Transform output or None if transform failed
        """
        if key in self._xsltLibrary and self.gateway_connected() and key in self._converters:
            return self._converters[key].transform(xml, self._parms(**kwargs))
        return None