def _range_rule(lbound, ubound) ->float:
    """
    Uses a modified version (dividing by 10 instead of 4) of
    the range rule heuristic to provide a very rough estimate
    of what a good standard deviation could be for a normal
    distribution to sample genetic mutations from for a
    hyperparameter having the range (lbound, ubound).
    """
    return (ubound - lbound) / 10
