public Document process(Document input) throws IOException, TransformerException {
        Document doc = Xml.copyDocument(input);
        includeFile(application, doc.getDocumentElement());
        return doc;
    }
Handles preprocess:include statements and returns a Document which has all the include statements resolved

@author hmusum
config-application-package/src/main/java/com/yahoo/config/application/IncludeProcessor.java