code: function fromCursor(cursor) {
    cursor = unbase64(cursor);
    cursor = cursor.substring(cursorPrefix.length, cursor.length);
    const [id, index] = cursor.split(cursorSeparator);
  
    return {
      id,
      index
    };
  }
docs: Decode a cursor into its component parts
  
  @param cursor
  @returns {{id, index}}