code: function traverseAllChildren(children, callback, traverseContext) {
    if (children == null) {
      return 0;
    }
  
    return traverseAllChildrenImpl(children, '', callback, traverseContext);
  }
docs: Traverses children that are typically specified as `props.children`, but
  might also be specified through attributes:
  
  - `traverseAllChildren(this.props.children, ...)`
  - `traverseAllChildren(this.props.leftPanelChildren, ...)`
  
  The `traverseContext` is an optional argument that is passed through the
  entire traversal. It can be used to store accumulations or anything else that
  the callback might find relevant.
  
  @param {?*} children Children tree object.
  @param {!function} callback To invoke upon traversing each child.
  @param {?*} traverseContext Context for traversal.
  @return {!number} The number of children in this subtree.