如何将数据帧转换为RDD[String，String]？

import org.apache.spark.sql.{Row, SparkSession}
import org.apache.spark.rdd.RDD

val spark = SparkSession.builder()
  .appName("DataFrame to RDD Conversion")
  .master("local")
  .getOrCreate()

val dataFrame = spark.read.format("csv")
  .option("header", "true")
  .load("path/to/input.csv")

val rdd: RDD[(String, String)] = dataFrame.rdd.map(row => {
  val column1 = row.getAs[String]("column1")
  val column2 = row.getAs[String]("column2")
  (column1, column2)
})

spark.stop()