How to use the navigation.Crumb function in navigation

getAnimation() {
        var {stateNavigator, unmountStyle, crumbStyle, sharedElements: getSharedElements} = this.props;
        var {state, data, oldState, oldData, oldUrl, crumbs, nextCrumb} = stateNavigator.stateContext;
        if (!oldState)
            return null;
        var {crumbs: oldCrumbs} = stateNavigator.parseLink(oldUrl);
        if (oldCrumbs.length < crumbs.length) {
            var {state: nextState, data: nextData} = crumbs.concat(nextCrumb)[oldCrumbs.length + 1];
            var enterAnim = unmountStyle(true, state, data, crumbs);
            var exitAnim = crumbStyle(false, oldState, oldData, oldCrumbs, nextState, nextData);
            var sharedElements = getSharedElements(state, data, crumbs);
        }
        if (crumbs.length < oldCrumbs.length) {
            var nextCrumb = new Crumb(oldData, oldState, null, null, false);
            var {state: nextState, data: nextData} = oldCrumbs.concat(nextCrumb)[crumbs.length + 1];
            var enterAnim = crumbStyle(true, state, data, crumbs, nextState, nextData);
            var exitAnim = unmountStyle(false, oldState, oldData, oldCrumbs);
            var oldSharedElements = getSharedElements(oldState, oldData, oldCrumbs);
        }
        if (crumbs.length === oldCrumbs.length) {
            var enterAnim = unmountStyle(true, state, data, crumbs);
            var exitAnim = unmountStyle(false, oldState, oldData, oldCrumbs, state, data);
        }
        return {enterAnim, exitAnim, sharedElements, oldSharedElements};
    }
    render() {