Objects implementing the NamedNodeMap interface are used to represent
collections of nodes that can be accessed by name. Note that NamedNodeMap
does not inherit from NodeList; NamedNodeMaps are not maintained in any
particular order. Objects contained in an object implementing NamedNodeMap
may also be accessed by an ordinal index, but this is simply to allow
convenient enumeration of the contents of a NamedNodeMap, and does not imply
that the DOM specifies an order to these Nodes.