getGroupedCharts() {
    return Apex._chartInstances
      .filter((ch) => {
        if (ch.group) {
          return true
        }
      })
      .map((ch) => (this.w.config.chart.group === ch.group ? ch.chart : this))
  }
Get charts in the same "group" (excluding the instance which is called upon) to perform operations on the other charts of the same group (eg., tooltip hovering)