def *(other)
      case other
      when Integer
        Duration.new(
          seconds: @seconds * other,
          months: @months * other
        )
      else
        raise ArgumentError, "Cannot multiply Duration #{self} by #{other.inspect}"
      end
    end
def *(other)
      case other
      when Integer
        Duration.new(
          seconds: @seconds * other,
          months: @months * other
        )
      else
        raise ArgumentError, "Cannot multiply Duration #{self} by #{other.inspect}"
      end
    end
Multiply a duration by a scalar.

 @param [Integer] other The scalar to multiply by.

 @return [Duration] The resulting duration with each component multiplied
   by the scalar.

 @example
   1.day * 7 == 1.week