Identifier of the second short-term outcome
s2(x)returns the input if this function is used directly. See `details` for more explanation
the second short-term outcome
This is a helperfunction used by multipredict() to identify the second
short-term outcome. It should not be called directly. If used directly it will only return the input. Therefore it should
not be called directly and only be used in the `formula` argument in multipredict()
to identify the variable that is the second short-term outcome. See `example` section of
multipredict() for more details.