get facets based on path variable

facets.xq

xquery version "3.1";

declare function local:get_facet ($books as element()*, $path as xs:string ) as element()?
{
  <binding>{
   
    
  for $book in $books 
    let $fld := $book/*[name()=$path]
    group by $f := $fld
    order by $f
    return element {$f} { attribute number {fn:count($book)}}  

  }</binding>
   
};

let $csv := fetch:text("https://gist.githubusercontent.com/CliffordAnderson/5be754415308dc407fc9/raw/daa23df71ceef375b83dd5b290284f83beeb710b/books.csv")
let $books := csv:parse($csv, map { 'header': true() })/csv/record
 return local:get_facet($books, "Binding" ) 
(: return ($book) :)