def METHOD_NAME(self, index=None):
    """Creates a cursor on the database.
    Creates a cursor on the database, which traverses the keys in their
    natural order.  It may be associated with an index, where it traverses
    the specified index's keys in their natural order.
    Args:
        index (str; optional) - an optional index; defaults to `None`
    Returns:
        (:obj:`Cursor`) - a Cursor instance
    """
    raise NotImplementedError()