code: function(nestedChildNodes, transaction, context) {
      var children = flattenChildren(nestedChildNodes);
      for (var name in children) {
        if (children.hasOwnProperty(name)) {
          var child = children[name];
          // The rendered children must be turned into instances as they're
          // mounted.
          var childInstance = instantiateReactComponent(child, null);
          children[name] = childInstance;
        }
      }
      return children;
    }
docs: Generates a "mount image" for each of the supplied children. In the case
  of `ReactDOMComponent`, a mount image is a string of markup.
  
  @param {?object} nestedChildNodes Nested child maps.
  @return {?object} A set of child instances.
  @internal