How to use the pywb.utils.loaders.load_yaml_config function in pywb

def load_yaml_file(self, root_dir, filename):
        filename = os.path.join(root_dir, filename)
        if os.path.isfile(filename):
            return load_yaml_config(filename)
        else:
            return {}

def load_rules(self, filename):
        config = load_yaml_config(filename)
        for rule in config.get('rules'):
            rule = self.parse_rewrite_rule(rule)
            if rule:
                self.rules.append(rule)

def create_wb_router(passed_config=None):
    passed_config = passed_config or {}

    defaults = load_yaml_config(DEFAULT_CONFIG)

    config = DictChain(passed_config, defaults)

    routes = []

    port = config.get('port')

    collections = config.get('collections', {})

    static_routes = config.get('static_routes', {})

    root_route = None

    # collections based on file system
    if config.get('enable_auto_colls', True):
        colls_loader_cls = config.get('colls_loader_cls', DirectoryCollsLoader)

def create_cdx_server_app(passed_config):
    """
    Create a cdx server api-only app
    For each collection, create a /-cdx access point
    which follows the cdx api
    """

    defaults = load_yaml_config(DEFAULT_CONFIG)

    config = DictChain(passed_config, defaults)

    collections = config.get('collections', {})

    static_routes = {}

    # collections based on file system
    if config.get('enable_auto_colls', True):
        colls_loader_cls = config.get('colls_loader_cls', DirectoryCollsLoader)
        dir_loader = colls_loader_cls(config, static_routes, collections)
        dir_loader()
        #collections.update(dir_loader())

    routes = []

def __init__(self, coll_name, colls_dir=None, must_exist=True):
        colls_dir = colls_dir or self.COLLS_DIR
        self.default_config = load_yaml_config(DEFAULT_CONFIG)

        if coll_name and not self.COLL_RX.match(coll_name):
            raise ValueError('Invalid Collection Name: ' + coll_name)

        self.colls_dir = os.path.join(os.getcwd(), colls_dir)

        self.change_collection(coll_name)

        if must_exist:
            self._assert_coll_exists()

def store_new(self, coll, path, mtime):
        """Load a collections metadata file and store it

        :param str coll: The name of the collection the metadata is for
        :param str path: The path to the collections metadata file
        :param float mtime: The current mtime of the collections metadata file
        :return: The collections metadata
        :rtype: dict
        """
        obj = load_yaml_config(path)
        self.cache[coll] = (mtime, obj)
        return obj