@Override
    public void processingInstruction(final String target, final String data) throws SAXException {
        if (handler != null) {
            handler.processingInstruction(target, data);
        } else if (passThrough) {
            super.processingInstruction(target, data);
        }
    }
@param target the processing instruction target
@param data   the processing instruction data, or null if none was supplied.
              The data does not include any whitespace separating it from
              the target
@throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
@see stroom.pipeline.filter.AbstractXMLFilter#processingInstruction(java.lang.String,
java.lang.String)
stroom-pipeline/src/main/java/stroom/pipeline/filter/XsltFilter.java