This should not usually be needed, however if you have a model that is slow
to fit, and upon visual inspection and/or trace analysis you determine that
during burn-in the samples had already approached the posterior distribution
then you can use this function to re-label samples from that point onwards
to be classed as adaptation samples.
This will allow them to be used in tests that check for the number of unique
samples, and in the building of the conditional distribution (which is used
for efficient sampling)
If all old samples do not match `from` then an error will be raised.