Infer an appropriate precision for _round_frac

def _infer_precision(base_precision, bins):
    """Infer an appropriate precision for _round_frac
    """
    for precision in range(base_precision, 20):
        levels = [_round_frac(b, precision) for b in bins]
        if algos.unique(levels).size == bins.size:
            return precision
    return base_precision