Using react-visjs-timeline, how are methods called to the Timeline ponent?

Methods like:

• timeline.fit();
• timeline.setItems({...});
• timeline.focus(id);

I added a ref to the ponent, but I'm not sure what item to call methods on:

<Timeline
  ref={this.timelineWrapperRef}
  options={this.state.options}
  items={this.state.items}
/>

The docs for react-visjs-timeline doesn't mention how to call methods.