Scala: DropDuplicates with non-numeric condition

//spark : My SparkSession
import spark.implicits._
  val df = Seq(
    (111111, "A", "True"),
    (111111, "A", "False"),
    (111111, "A", "False"),
    (222222, "B", "False"),
    (222222, "B", "False"),
    (333333, "C", "True"),
    (333333, "C", "True"),
    (333333, "C", "Unsure")
  ).toDF("item_id", "location_id", "decision")

  df.printSchema()
  /** root
    * |-- item_id: integer (nullable = false)
    * |-- location_id: string (nullable = true)
    * |-- decision: string (nullable = true)
    */