TODO: ranme to datetimestr

def unixtime_to_datetimestr(unixtime, timefmt='%Y/%m/%d %H:%M:%S', isutc=True):
    """
    TODO: ranme to datetimestr
    """
    try:
        if unixtime == -1:
            return 'NA'
        if unixtime is None:
            return None
        if isutc:
            return datetime.datetime.utcfromtimestamp(unixtime).strftime(timefmt)
        else:
            return datetime.datetime.fromtimestamp(unixtime).strftime(timefmt)
    except ValueError:
        raise