public function toByteStream(Swift_InputByteStream $is)
{
if (count($children = $this->getChildren()) > 0 && $this->getBody() != '') {
$this->setChildren(array_merge(array($this->becomeMimePart()), $children));
parent::toByteStream($is);
$this->setChildren($children);
} else {
parent::toByteStream($is);
}
}