docs: function ViewportNavigationInterceptor(spec) {
      // ---------------------------------------------- input arguments processing
  
      if (spec == null) {
          spec = {};
      }
  
      // -------------------------------------------------------------- processing
  
      var finalSpec = ariaUtilsObject.assign({}, spec, {
          origin: 'browser',
  
          getReferenceElement: function () {
              return document.body;
          },
  
          focusTraps: [
              // first
              {
                  direction: 'forward',
                  insert: insertFirst
              },
              // last
              {
                  direction: 'backward',
                  insert: insertLast
              }
          ]
      });
  
      // ------------------------------------------------------------------ return
  
      return NavigationInterceptor(finalSpec);
  }