code: function tabbableElementsNodeFilter(node) {
          var nodeStyle = _ElementUtilities._getComputedStyle(node);
          if (nodeStyle.display === "none" || nodeStyle.visibility === "hidden") {
              return _Global.NodeFilter.FILTER_REJECT;
          }
          if (node._tabContainer) {
              return _Global.NodeFilter.FILTER_ACCEPT;
          }
          if (node.parentNode && node.parentNode._tabContainer) {
              var managedTarget = node.parentNode._tabContainer.childFocus;
              // Ignore subtrees that are under a tab manager but not the child focus. If a node is contained in the child focus, either accept it (if it's tabbable itself), or skip it and find tabbable content inside of it.
              if (managedTarget && node.contains(managedTarget)) {
                  return (getTabIndex(node) >= 0 ? _Global.NodeFilter.FILTER_ACCEPT : _Global.NodeFilter.FILTER_SKIP);
              }
              return _Global.NodeFilter.FILTER_REJECT;
          }
          var tabIndex = getTabIndex(node);
          if (tabIndex >= 0) {
              return _Global.NodeFilter.FILTER_ACCEPT;
          }
          return _Global.NodeFilter.FILTER_SKIP;
      }
docs: tabbableElementsNodeFilter works with the TreeWalker to create a view of the DOM tree that is built up of what we want the focusable tree to look like. When it runs into a tab contained area, it rejects anything except the childFocus element so that any potentially tabbable things that the TabContainer doesn't want tabbed to get ignored.