public function year_range($start_year = 0, $separator = ' - ')
    {

        if(! is_numeric($start_year)){
            throw new InvalidArgumentException("Invalid Argument Format passed . It should be a number");
        }

        if( $start_year < 0){
            throw new InvalidArgumentException("Invalid Argument passed {$start_year} . It shouldn't be a negative value");
        }

        if( $start_year == 0){
            return $this->current_year();
        }

      return ($start_year == $this->current_year()) ? $this->current_year() : $start_year . $separator . $this->current_year();
    }