How to use the espree.VisitorKeys function in espree

eventGenerator = new CommentEventGenerator(eventGenerator, sourceCode);

            /*
             * Each node has a type property. Whenever a particular type of node is found,
             * an event is fired. This allows any listeners to automatically be informed
             * that this type of node has been found and react accordingly.
             */
            controller.traverse(ast, {
                enter: function(node, parent) {
                    node.parent = parent;
                    eventGenerator.enterNode(node);
                },
                leave: function(node) {
                    eventGenerator.leaveNode(node);
                },
                keys: espree.VisitorKeys
            });
        }

        // sort by line and column
        messages.sort(function(a, b) {
            var lineDiff = a.line - b.line;

            if (lineDiff === 0) {
                return a.column - b.column;
            } else {
                return lineDiff;
            }
        });

        return messages;
    };

// save config so rules can access as necessary
            currentConfig = config;
            controller = new estraverse.Controller();

            ecmaFeatures = currentConfig.parserOptions.ecmaFeatures || {};
            ecmaVersion = currentConfig.parserOptions.ecmaVersion || 5;

            // gather data that may be needed by the rules
            scopeManager = escope.analyze(ast, {
                ignoreEval: true,
                nodejsScope: ecmaFeatures.globalReturn,
                impliedStrict: ecmaFeatures.impliedStrict,
                ecmaVersion: ecmaVersion,
                sourceType: currentConfig.parserOptions.sourceType || "script",
                childVisitorKeys: espree.VisitorKeys,
                fallback: "none"
            });
            currentScopes = scopeManager.scopes;

            /*
             * Index the scopes by the start range of their block for efficient
             * lookup in getScope.
             */
            scopeMap = [];
            currentScopes.forEach(function(scope, index) {
                var range = scope.block.range[0];

                // Sometimes two scopes are returned for a given node. This is
                // handled later in a known way, so just don't overwrite here.
                if (!scopeMap[range]) {
                    scopeMap[range] = index;