shareTitle (shareTitle) {
        if (!arguments.length) {
            return this._shareTitle;
        }
        this._shareTitle = shareTitle;
        return this;
    }
Get or set title sharing for the chart. If set, the {@link BaseMixin#title .title()} value from
this chart will be shared with composed children.

Note: currently you must call this before `compose` or the child will still get the parent's
`title` function!
@param {Boolean} [shareTitle=true]
@returns {Boolean|CompositeChart}