highcharts, use external function but get highcharts data

I’m using highcharts in angular and trying to configure a personal tooltip.

My problem is I need to use the data that I have in my angular component and the point selected in the tooltip, so, if I use this structure:

pointFormatter: function () {
     // here I have this.x and this.y as the selected point
     // but I have no access to external functions
}

and if I use this one:

pointFormatter: () => {
  // here I have access to external functions
  // but I have no access to the selected point
}

How can I do it to have access to both to be able to calculate my tooltip?

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Source Url highcharts, use external function but get highcharts data