docs: def _convert_markup_images(self, soup):
          """
          Convert images of instructions markup. Images are downloaded,
          base64-encoded and inserted into <img> tags.
  
          @param soup: BeautifulSoup instance.
          @type soup: BeautifulSoup
          """
          # 6. Replace <img> assets with actual image contents
          images = [image for image in soup.find_all('img')
                    if image.attrs.get('assetid') is not None]
          if not images:
              return
  
          # Get assetid attribute from all images
          asset_ids = [image.attrs.get('assetid') for image in images]
          self._asset_retriever(asset_ids)
  
          for image in images:
              # Encode each image using base64
              asset = self._asset_retriever[image['assetid']]
              if asset.data is not None:
                  encoded64 = base64.b64encode(asset.data).decode()
                  image['src'] = 'data:%s;base64,%s' % (
                      asset.content_type, encoded64)