/**
  * Invoke the Emailer's ::doSend method.
  *
  * @param EmailInterface $email
  * @return boolean
  */
 public function send(EmailInterface $email)
 {
     foreach ($this->writers as $writer) {
         $content = $email->accept($writer);
         if ($content !== null) {
             return $this->doSend($content, $email);
         }
     }
     throw new \RuntimeException("No visit method for " . get_class($email) . " found among writers.");
 }