def connect(self): 
        try:
            self.connection = pymongo.Connection(self.host, self.port)
            self.db = self.connection[self.name]
        except AutoReconnect:
            raise DatabaseException("It's not possible connect to the database")
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()