def stddev(li, mean):
    if not li:
        return None
    return math.sqrt(sum(x*x for x in li) - mean*mean)
Extract the latitude from an XPath to a Google Map.
dataset/ETHPy150Open artirix/logcabin/logcabin/statistics.py/stddev--crossover with--dataset/ETHPy150Open tryolabs/daywatch/daywatch/core/scraper/item_scraper/extractors.py/lat