def __repr__(self):
        return "<Requirements({})>".format(self.filename.name or "")
def test_impl(n):
            df1 = pd.DataFrame({'key1': np.arange(n), 'A': np.arange(n) + 1.0})
            df2 = pd.DataFrame({'key2': n - np.arange(n), 'A': n + np.arange(n) + 1.0})
            A3 = pd.concat([df1.A, df2.A])
            return A3.sum()