Shifts all siblings with B<positions values> in the range @between
(inclusive) by one position as specified by $direction (left if < 0,
right if > 0). By default simply increments/decrements each
-L<position_column> value by 1, doing so in a way as to not violate
+L</position_column> value by 1, doing so in a way as to not violate
any existing constraints.
Note that if you override this method and have unique constraints
-including the L<position_column> the shift is not a trivial task.
+including the L</position_column> the shift is not a trivial task.
Refer to the implementation source of the default method for more
information.