trait  Option[A] {
  def flatMap[B](f: A =>  Option[B]): Option[B]
  def map[B](f: A => B): Option[B]
}

case class None[A]() extends Option[A] {
  def flatMap[B](f: A => Option[B]): Option[B] = None[B]
  def map[B](f: A => B): Option[B] = None[B]
}

// return the give parameter wrapped in option
def unit[T](aType: T):  Option[T] = Some(aType)

case class Some[A](a: A) extends  Option[A] {
  def flatMap[B](f: A => Option[B]):  Option[B] = f(a)
  def map[B](f: A => B): Option[B] = unit(f(a))
}