@Override
    protected DocumentProcessor doBuild(DeployState deployState, TreeConfigProducer<AnyConfigProducer> ancestor, Element documentProcessorElement) {
        DocumentProcessorModelBuilder modelBuilder = new DocumentProcessorModelBuilder(documentProcessorElement);
        return new DocumentProcessor(modelBuilder.build());
    }
Builds a DocumentProcessor from XML.

@author gjoranv
config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/chains/docproc/DomDocumentProcessorBuilder.java