code: def LoadFromStorage(path, product_yaml_key, required_client_values,
                      optional_product_values):
    
  
    if not os.path.isabs(path):
      path = os.path.expanduser(path)
  
    try:
      with open(path, 'rb') as handle:
        yaml_doc = handle.read()
    except IOError:
      raise googleads.errors.GoogleAdsValueError(
          'Given yaml file, %s, could not be opened.' % path)
  
    try:
      client_kwargs = LoadFromString(yaml_doc, product_yaml_key,
                                     required_client_values,
                                     optional_product_values)
    except googleads.errors.GoogleAdsValueError as e:
      raise googleads.errors.GoogleAdsValueError(
          'Given yaml file, %s, could not find some keys. %s' % (path, e))
  
    return client_kwargs
docs: Loads the data necessary for instantiating a client from file storage.
  
    In addition to the required_client_values argument, the yaml file must supply
    the keys used to create OAuth2 credentials. It may also optionally set proxy
    configurations.
  
    Args:
      path: A path string to the yaml document whose keys should be used.
      product_yaml_key: The key to read in the yaml as a string.
      required_client_values: A tuple of strings representing values which must
        be in the yaml file for a supported API. If one of these keys is not in
        the yaml file, an error will  be raised.
      optional_product_values: A tuple of strings representing optional values
        which may be in the yaml file.
  
    Returns:
      A dictionary map of the keys in the yaml file to their values. This will not
      contain the keys used for OAuth2 client creation and instead will have a
      GoogleOAuth2Client object stored in the 'oauth2_client' field.
  
    Raises:
      A GoogleAdsValueError if the given yaml file does not contain the
      information necessary to instantiate a client object - either a
      required_client_values key was missing or an OAuth2 key was missing.