MessageBuilder/NewThreadMessageBuilder.php
/**
     * @param ParticipantInterface $recipient
     *
     * @return NewThreadMessageBuilder (fluent interface)
     */
@param ParticipantInterface $recipient
@return NewThreadMessageBuilder (fluent interface)
@param ParticipantInterface $recipient @return NewThreadMessageBuilder ( fluent interface )
public function addRecipient(ParticipantInterface $recipient): NewThreadMessageBuilder
    {
        $this->thread->addParticipant($recipient);
        return $this;
    }
public function addRecipient ( ParticipantInterface $ recipient ) : NewThreadMessageBuilder { $ this -> thread -> addParticipant ( $ recipient ) ; return $ this ; }
@param ParticipantInterface $recipient
 @return NewThreadMessageBuilder (fluent interface)
@param ParticipantInterface $recipient @return NewThreadMessageBuilder ( fluent interface )