def most_common(self, n=None):
        if n is None:
            return sorted(self.iteritems(), key=itemgetter(1), reverse=True)
        return nlargest(n, self.iteritems(), key=itemgetter(1))
List the n most common elements and their counts from the most
dataset/ETHPy150Open dbcli/pgcli/pgcli/packages/counter.py/Counter.most_common