Scala: Occurrences with pairs, groupBy and map

occurrences2.scala

/**
  * For each unique character in the list `chars`, it calculates the number of
  * times it occurs. times(List('a', 'b', 'a')) should return List(('a', 2), ('b', 1))
  */
def howManyTimes(w: String): List[(Char, Int)] = {
  val grouped = w.groupBy(x => x.toLower) // Group by element (all chars to lowercase)
  grouped.map(x => (x._1, x._2.length)).toList // Create pair for each element
}