public function addSupplementaryAgreements(\AgentSIB\Diadoc\Api\Proto\Events\SupplementaryAgreementAttachment $value)
    {
        if ($this->SupplementaryAgreements === null) {
            $this->SupplementaryAgreements = new \Protobuf\MessageCollection();
        }

        $this->SupplementaryAgreements->add($value);
    }