<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _mutate_probability_vec(probability_vec, mutation_chance, mutation_adjust_rate):
 """Randomly adjust probabilities. WARNING: Modifies probability_vec argument. """

    bits_to_mutate = numpy.random.random(probability_vec.size) <= mutation_chance
    probability_vec[bits_to_mutate] = _adjust(
        probability_vec[bits_to_mutate],
        numpy.random.random(numpy.sum(bits_to_mutate)), mutation_adjust_rate)