How to get string Values on x-Axis on stacked Bar Chart in Charts API

I was trying to achieve String values on x-axis of stacked Bar Chart
and always end up having Double Values

## What did you do?
I have entered the following for X-axis
var xAxis = barChart.xAxis
xAxis.labelPosition = .bottom
var xAxis = barChart.xAxis
xAxis.labelPosition = .bottom
xAxis.labelFont = .systemFont(ofSize: 10)
xAxis.granularity = 1
xAxis.labelCount = 7
xAxis.valueFormatter = DefaultAxisValueFormatter(formatter: formatter)

## What did you expect to happen?
I want to have have string value to be there as mentioned in BarChart

## Charts Environment

**Latest Chart Version:**
**10.2.1:**
**4.2:**
**Swift:**
**macOS version running Xcode:**