code: def _mutate_probability_vec(probability_vec, mutation_chance, mutation_adjust_rate):
      
      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)
docs: Randomly adjust probabilities.
  
      WARNING: Modifies probability_vec argument.