How to use the siphon.catalog.Dataset function in siphon

resolver_url = resolver_base + self.url_path
            resolver_xml = session_manager.urlopen(resolver_url)
            tree = ET.parse(resolver_xml)
            root = tree.getroot()
            if 'name' in root.attrib:
                self.catalog_name = root.attrib['name']
            else:
                self.catalog_name = 'No name found'
            resolved_url = ''
            found = False
            for child in root.iter():
                if not found:
                    tag_type = child.tag.split('}')[-1]
                    if tag_type == 'dataset':
                        if 'urlPath' in child.attrib:
                            ds = Dataset(child)
                            resolved_url = ds.url_path
                            found = True
            if found:
                return resolved_url
            else:
                log.warning('no dataset url path found in latest.xml!')

def _process_dataset(self, element):
        catalog_url = ''
        if 'urlPath' in element.attrib:
            if element.attrib['urlPath'] == 'latest.xml':
                catalog_url = self.catalog_url

        ds = Dataset(element, catalog_url=catalog_url)
        self.datasets[ds.name] = ds