code: @Override
      public Document createDocument(Document parentDocument) {
          Ruby runtime = JRubyRuntimeContext.get(parentDocument);
          RubyHash options = RubyHash.newHash(runtime);
          options.put(
                  runtime.newSymbol("parent"),
                  ((DocumentImpl) parentDocument).getRubyObject());
  
          return (Document) NodeConverter.createASTNode(runtime, NodeConverter.NodeType.DOCUMENT_CLASS, runtime.getNil(), options);
      }
docs: Creates an inner document for the given parent document.
  Inner documents are used for tables cells with style {@code asciidoc}.
  
  @param parentDocument The parent document of the new document.
  @return A new inner document.