Gather the sub-elements attached to a node

        Gather rdf:Bag and and rdf:Seq into set and list respectively. For
        alternate languages values, take the first language only for
        simplicity.

def _get_subelements(self, node):
        """Gather the sub-elements attached to a node

        Gather rdf:Bag and and rdf:Seq into set and list respectively. For
        alternate languages values, take the first language only for
        simplicity.
        """
        items = node.find('rdf:Alt', self.NS)
        if items is not None:
            try:
                return items[0].text
            except IndexError:
                return ''

        for xmlcontainer, container, insertfn in XMP_CONTAINERS:
            items = node.find('rdf:{}'.format(xmlcontainer), self.NS)
            if items is None:
                continue
            result = container()
            for item in items:
                insertfn(result, item.text)
            return result
        return ''