parse `userlist` sections, and return a config.Userlist

def build_userlist(self, userlist_node):
        """parse `userlist` sections, and return a config.Userlist"""
        proxy_name = userlist_node.userlist_header.proxy_name.text
        config_block_lines = self.__build_config_block(
            userlist_node.config_block)
        return config.Userlist(
            name=proxy_name,
            config_block=config_block_lines)