docs: def import_oauth2_credentials(filename=STORAGE_FILENAME):
      """Import OAuth 2.0 session credentials from storage file.
      Parameters
          filename (str)
              Name of storage file.
      Returns
          credentials (dict)
              All your app credentials and information
              imported from the configuration file.
      """
      with open(filename, 'r') as storage_file:
          storage = safe_load(storage_file)
  
      # depending on OAuth 2.0 grant_type, these values may not exist
      client_secret = storage.get('client_secret')
      refresh_token = storage.get('refresh_token')
  
      credentials = {
          'access_token': storage['access_token'],
          'client_id': storage['client_id'],
          'client_secret': client_secret,
          'expires_in_seconds': storage['expires_in_seconds'],
          'grant_type': storage['grant_type'],
          'refresh_token': refresh_token,
          'scopes': storage['scopes'],
      }
  
      return credentials