Function with_node_qname 

pub fn with_node_qname<R, FnR>(node: &Node, caller: FnR) -> R
where
    FnR: FnOnce(&str) -> R,

Borrow a node’s qualified name (ltx:section, #PCDATA, …) as a &str for the duration of caller.

The closure form is the point: qnames are interned, and lending the arena’s copy lets a caller compare or match on the name without the String that get_node_qname + to_string would allocate on every node of a walk.