How to use the v-tooltip.VTooltip.options function in v-tooltip

import { HandleDirective } from 'vue-slicksort';
Vue.directive('sort-handle', HandleDirective);

// https://github.com/rigor789/vue-scrollto
import VueScrollTo from 'vue-scrollto';
Vue.use(VueScrollTo, {
    container: 'main',
});

// https://github.com/katlasik/mime-matcher
import MimeMatcher from 'mime-matcher';
Vue.prototype.MimeMatcher = MimeMatcher;

// https://github.com/Akryum/v-tooltip
import { VTooltip } from 'v-tooltip';
VTooltip.options.defaultPlacement = 'bottom';
Vue.directive('tooltip', VTooltip);

import 'vueleton/lib/dropdown.css';
import { ClientTable } from 'vue-tables-2';
import moment from 'moment';
import DynamoDb from 'aws-sdk/clients/dynamodb';
import { VTooltip } from 'v-tooltip';
import * as d3 from 'd3';
import model from '../assets/TrackingBotModel.json';
import StackedBar from './StackedBar';
import Logger from '../logger';

/* Stores RadialProgressChart instances to use on updates */
const charts = {};

/* eslint-disable no-new, no-alert, max-len, no-loop-func */

VTooltip.options.defaultClass = 'my-tooltip';
Vue.component('detail-chart', StackedBar);
Vue.component('dropdown', Dropdown);
Vue.use(ClientTable, {
},
);

/* eslint-disable no-var, no-plusplus */

/* Computes text value to use for center of radial chart
   This value will be updated as data for the radial chart is also
   updated. The center of the chart shows a text value that corresponds to the
   current day, or week, and/or monthly percentage. If a daily target is
   specified, then the center text represents the percent complete for each
   day. if a weekly target is specified, the center text is a percent completed
   for the week. if a monthly target is specified, the center text is a percent
   complete for the month.