如何使用iOS的图表库在PieChart中显示字符串标签？

import Charts

// 准备数据源
let dataEntries = [
    PieChartDataEntry(value: 30, label: "标签1"),
    PieChartDataEntry(value: 40, label: "标签2"),
    PieChartDataEntry(value: 20, label: "标签3"),
    PieChartDataEntry(value: 10, label: "标签4")
]

// 创建PieChart
let pieChart = PieChartView(frame: CGRect(x: 0, y: 0, width: 300, height: 300))

// 设置属性
pieChart.drawEntryLabelsEnabled = true

// 添加数据
let dataSet = PieChartDataSet(entries: dataEntries, label: "")
let data = PieChartData(dataSet: dataSet)
pieChart.data = data

// 自定义标签样式
dataSet.valueFont = UIFont.systemFont(ofSize: 12)
dataSet.valueTextColor = UIColor.black

// 将PieChart添加到视图中
view.addSubview(pieChart)