Since the dataset viewer uses dataset streaming to show the first rows of your dataset, you have to make the dataset compatible with streaming for the preview to work.
However `xml.dom.minidom.parse` does not support streaming out-of-the-box (it can't read a remote file). To fix it, you need to `open` the file first, before passing it to `xml.dom.minidom.parse`.
This works because `open` in the dataset script is extended to support reading remote files over HTTP, especially to enable streaming.
