public function boundaries(): ?Period
    {
        $period = reset($this->intervals);
        if (false === $period) {
            return null;
        }

        return $period->merge(...$this->intervals);
    }
public function boundaries(): ?Period
    {
        $period = reset($this->intervals);
        if (false === $period) {
            return null;
        }

        return $period->merge(...$this->intervals);
    }
public function boundaries ( ) : ? Period { $ period = reset ( $ this -> intervals ) ; if ( false === $ period ) { return null ; } return $ period -> merge ( ... $ this -> intervals ) ; }
Returns the sequence boundaries as a Period instance.

If the sequence contains no interval null is returned.

@return ?Period
Returns the sequence boundaries as a Period instance .