Same as format_time() but always uses SI-prefix and 3 significant figures.

def format_time_small(seconds):
    """
    Same as format_time() but always uses SI-prefix and 3 significant figures.
    """

    if not isinstance(seconds, (int, float)):
        return str(seconds)

    if math.isnan(seconds):
        return "-"

    if abs(seconds)<1:
        milliseconds = 1000*seconds
        if abs(milliseconds)<1:
            microseconds = 1000*milliseconds
            if abs(microseconds)<1:
                nanoseconds = 1000*microseconds
                if abs(nanoseconds)<0.5:
                    return "0"
                else:
                    return "{:.0f}ns".format(nanoseconds)
            elif abs(microseconds)<10:
                return "{:.2f}us".format(microseconds)
            elif abs(microseconds)<100:
                return "{:.1f}us".format(microseconds)
            else:
                return "{:.0f}us".format(microseconds)
        elif abs(milliseconds)<10:
            return "{:.2f}ms".format(milliseconds)
        elif abs(milliseconds)<100:
            return "{:.1f}ms".format(milliseconds)
        else:
            return "{:.0f}ms".format(milliseconds)
    elif abs(seconds)<10:
            return "{:.2f}s".format(seconds)
    elif abs(seconds)<100:
        return "{:.1f}s".format(seconds)
    else:
        return "{:.0f}s".format(seconds)