'Update prefetch count after pool/shrink grow operations.
Index must be the change in number of processes as a positive
(increasing) or negative (decreasing) number.
Note:
Currently pool grow operations will end up with an offset
of +1 if the initial size of the pool was 0 (e.g.
:option:`--autoscale=1,0 <celery worker --autoscale>`).'

def _update_prefetch_count(self, index=0):

    num_processes = self.pool.num_processes
    if ((not self.initial_prefetch_count) or (not num_processes)):
        return
    self.initial_prefetch_count = (self.pool.num_processes * self.prefetch_multiplier)
    return self._update_qos_eventually(index)
