dist/claygl.es.js
function (callback, context) {
        callback.call(context, this);
        var _children = this._children;
        for(var i = 0, len = _children.length; i < len; i++) {
            _children[i].traverse(callback, context);
        }
    }
function (callback, context) {
        callback.call(context, this);
        var _children = this._children;
        for(var i = 0, len = _children.length; i < len; i++) {
            _children[i].traverse(callback, context);
        }
    }
function ( callback , context ) { callback . call ( context , this ) ; var _children = this . _children ; for ( var i = 0 , len = _children . length ; i < len ; i ++ ) { _children [ i ] . traverse ( callback , context ) ; } }
Depth first traverse all its descendant scene nodes.

**WARN** Don't do `add`, `remove` operation in the callback during traverse.
@param {Function} callback
@param {Node} [context]
Depth first traverse all its descendant scene nodes .