protected function getBlock(\DOMElement $element) {
    $block = '';
    /** @var \DOMNode $node */
    foreach ($element->childNodes as $node) {
      switch ($node->nodeType) {

        case XML_ELEMENT_NODE:
          /** @var \DOMElement $node */
          switch ($node->nodeName) {

            // Explicitly handle these elements.

            case 'i':
            case 'em':
              $block .= '*' . $this->getBlock($node) . '*';
              break;

            case 'b':
            case 'strong':
              $block .= '**' . $this->getBlock($node) . '**';
              break;

            case 'a':
              if ($node->hasAttribute('href')) {
                $block .= '[' . $this->getBlock($node) . ']' .
                  '(' . $node->getAttribute('href') . ')';
              }
              break;

            // Other inline elements.
            default:
              // Recursively handle any descendant elements we care about.
              $block .= $this->getBlock($node);
              break;

          }
          break;

        case XML_TEXT_NODE:
          /** @var \DOMText $node */
          $block .= self::escape($node->textContent);
          break;

      }
    }

    // Handle white-listed elements.
    if (in_array($element->nodeName, $this->white_list)) {
      $tag = $element->cloneNode();
      if (!empty($block)) {
        $tag->appendChild(new \DOMText($block));
      }
      $block = $this->dom->saveXML($tag);
    }

    return $block;
  }