def exportValue(self, vf, value):
        m = StrStrHashMap(value)
        keysAndValues = []
        for i in m.keys():
            keysAndValues.append(i)
            keysAndValues.append(m[i])
def test_impl(n):
            df = pd.DataFrame({'A': np.arange(n)})
            df.A[2] = 0
            return df.A.nunique()