def most_common(self, n=None):
        if n is None:
            return sorted(iteritems(self), key=itemgetter(1), reverse=True)
        return nlargest(n, iteritems(self), key=itemgetter(1))
List the n most common elements and their counts from the most
dataset/ETHPy150Open PythonCharmers/python-future/docs/3rd-party-py3k-compat-code/pandas_py3k.py/_Counter.most_common