private void configureMessageListener(final TransformerImpl transformer) {
        try {
            NullSafe.consume(
                    transformer,
                    TransformerImpl::getUnderlyingXsltTransformer,
                    xsltTransformer ->
                            xsltTransformer.setMessageListener(this::onXsltMessage));
        } catch (Exception e) {
            // Just log and swallow as the message listener is not critical
            LOGGER.error("Error configuring XSLT message listener: " + e.getMessage(), e);
        }
    }
@throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
@see #startDocument
@see stroom.pipeline.filter.AbstractXMLFilter#endDocument()
stroom-pipeline/src/main/java/stroom/pipeline/filter/XsltFilter.java