def direction(direction, allow_bi=False):
    """Validate that the given direction is one of the allowed constants.

    If ``allow_bi`` is ``True`` then ``Direction.BIDIRECTIONAL`` is
    acceptable.
    """
    valid = [Direction.CAUSE, Direction.EFFECT]
    if allow_bi:
        valid.append(Direction.BIDIRECTIONAL)

    if direction not in valid:
        raise ValueError('`direction` must be one of {}'.format(valid))

    return True
def direction ( direction , allow_bi = False ) : valid = [ Direction . CAUSE , Direction . EFFECT ] if allow_bi : valid . append ( Direction . BIDIRECTIONAL ) if direction not in valid : raise ValueError ( '`direction` must be one of {}' . format ( valid ) ) return True
Validate that the given direction is one of the allowed constants.

    If ``allow_bi`` is ``True`` then ``Direction.BIDIRECTIONAL`` is
    acceptable.