obj[[i]]
"[.XMLNode"(obj, ...)
"[[.XMLNode"(obj, ...)
"[[.XMLDocumentContent"(obj, ...)XMLDocumentContent is the container for the top-level node that also contains information
such as the URI/filename and XML version. This accessorlink{[} and link{[[} operatorsobj
and identified by ....xmlAttrs
[<-.XMLNode
[[<-.XMLNode