function getNodeFromInstance(instance) {
  var id = ReactInstanceMap.get(instance)._rootNodeID;
  if (ReactEmptyComponentRegistry.isNullComponentID(id)) {
    return null;
  }
  if (!nodeCache.hasOwnProperty(id) || !isValid(nodeCache[id], id)) {
    nodeCache[id] = ReactMount.findReactNodeByID(id);
  }
  return nodeCache[id];
}
Finds the node with the supplied public React instance.

@param {*} instance A public React instance.
@return {?DOMElement} DOM node with the suppled `id`.
@internal