document method
Implementation
@override
Parser document() => super.document().castList<dynamic>().map((each) {
final nodes = [];
if (each[0] != null) {
nodes.add(each[0]); // declaration
}
nodes.addAll(each[1]);
if (each[2] != null) {
nodes.add(each[2]); // doctype
}
nodes.addAll(each[3]);
nodes.add(each[4]); // document
nodes.addAll(each[5]);
return createDocument(nodes.cast<TNode>());
});