A detailed description of working with JET elements and classes in your typescript project can be found at:
JET Typescript Usage.
JET Timeline Series
The oj-timeline-series element is used to declare properties for timeline series and is only valid as the
child of a template element for the seriesTemplate slot of oj-timeline.
<oj-timeline data="[[dataProvider]]">
<template slot="seriesTemplate">
<oj-timeline-series
label="[[$current.items[0].data.series]]">
</oj-timeline-series>
</template>
</oj-timeline>