Option#contains
だまされそうになった
object Option { ... /** Tests whether the option contains a given value as an element. * * @example {{{ * // Returns true because Some instance contains string "something" which equals "something". * Some("something") contains "something" * * // Returns false because "something" != "anything". * Some("something") contains "anything" * * // Returns false when method called on None. * None contains "anything" * }}} * * @param elem the element to test. * @return `true` if the option has an element that is equal (as * determined by `==`) to `elem`, `false` otherwise. */ final def contains[A1 >: A](elem: A1): Boolean = !isEmpty && this.get == elem