def valid? number
      raise_on_type_mismatch number
      num, check = split_number(number)
      self.of(num) == check
    end
def valid? number
      raise_on_type_mismatch number
      num, check = split_number(number)
      self.of(num) == check
    end
Primitive97 validation of provided number

 @example
   Sjekksum::Primitive97.valid?(235695) #=> true

 @param  number [Integer, String] number with included checksum

 @return [Boolean]