@Override
    public void processingInstruction(final String target, final String data) throws SAXException {
        // Ensure we have started a document - this avoids some unexpected behaviour in XMLParser where we
        // receive processing instruction events before a startDocument() event, see gh-225.
        startDocument();

        handler.processingInstruction(target, data);
        super.processingInstruction(target, data);
    }
Buffers a processingInstruction event if buffer is set to true.

@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 SAXException Not thrown.
@see stroom.pipeline.filter.AbstractXMLFilter#processingInstruction(java.lang.String,
java.lang.String)
stroom-pipeline/src/main/java/stroom/pipeline/filter/TinyTreeBufferFilter.java