Skelton class of Visitor.
You can override the following methods and implement the other "visit_TYPE" methods.
You should implement some "visit_name_NAME" methods and "method_missing" method for accept_name.
Visitor#visit_Document(grove, *rest)
callback method.
Visitor#visit_Element(element, *rest)
callback method.
Visitor#visit_Text(text, *rest)
callback method.
Visitor#visit_CDATASection(text, *rest)
callback method.
Visitor#visit_Comment(comment, *rest)
callback method.
Visitor#visit_ProcessingInstruction(pi, *rest)
callback method.
XML::Grove::Visitor like interfaces.
Node#accept(visitor, *rest)
call back visit_* method.
Node#accept_name(visitor, *rest)
call back visit_name_* method.
Node#children_accept(visitor, *rest)
for each children, call back visit_* methods.
Node#children_accept_name(visitor, *rest)
for each children, call back visit_name_* method.
Node#each
iterator interface.