A demonstration of doctests

doctests.py

def threshold_above(hist, threshold_value):
    """
    >>> threshold_above(collections.Counter({518: 10, 520: 20, 530: 20, 525: 17}), 15)
    [520, 530, 525]
    """
    if not isinstance(hist,collections.Counter):
        raise ValueError("requires collections.Counter")
   
    above = [k for k, v in hist.items() if v > threshold_value]
    return above