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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _conn_key(self, instance, db_key, db_name=None):
        ''' Return a key to use for the connection cache
        '''
        dsn, host, username, password, database, driver = self._get_access_info(instance, db_key, db_name)
        return '{}:{}:{}:{}:{}:{}'.format(dsn, host, username, password, database, driver)