docs: function(id) {
      var reactRootID = ReactInstanceHandles.getReactRootIDFromNodeID(id);
      var container = containersByReactRootID[reactRootID];
  
      if ("production" !== process.env.NODE_ENV) {
        var rootElement = rootElementsByReactRootID[reactRootID];
        if (rootElement && rootElement.parentNode !== container) {
          ("production" !== process.env.NODE_ENV ? invariant(
            // Call internalGetID here because getID calls isValid which calls
            // findReactContainerForID (this function).
            internalGetID(rootElement) === reactRootID,
            'ReactMount: Root element ID differed from reactRootID.'
          ) : invariant(// Call internalGetID here because getID calls isValid which calls
          // findReactContainerForID (this function).
          internalGetID(rootElement) === reactRootID));
  
          var containerChild = container.firstChild;
          if (containerChild &&
              reactRootID === internalGetID(containerChild)) {
            // If the container has a new child with the same ID as the old
            // root element, then rootElementsByReactRootID[reactRootID] is
            // just stale and needs to be updated. The case that deserves a
            // warning is when the container is empty.
            rootElementsByReactRootID[reactRootID] = containerChild;
          } else {
            ("production" !== process.env.NODE_ENV ? warning(
              false,
              'ReactMount: Root element has been removed from its original ' +
              'container. New container:', rootElement.parentNode
            ) : null);
          }
        }
      }
  
      return container;
    }