public function includes(PeriodInterface $period, $strict = true)
    {
        if (true === $strict) {
            return $this->getBegin() <= $period->getBegin() && $this->getEnd() >= $period->getEnd();
        }

        return
            $this->includes($period, true) ||
            $period->includes($this, true) ||
            $this->contains($period->getBegin()) ||
            $this->contains($period->getEnd())
        ;
    }