def human_readable_time(time_ps: int) ->str:
    """Transform **time_ps** to a human readable string.

    Args:
        time_ps (int): Time in pico seconds.

    Returns:
        str: Human readable time.
    """
    time_units = ['femto seconds', 'pico seconds', 'nano seconds',
        'micro seconds', 'mili seconds']
    t = time_ps * 1000
    for tu in time_units:
        if t < 1000:
            return str(t) + ' ' + tu
        t /= 1000
    return str(time_ps)
