How to use the cflib.crazyflie.syncLogger.SyncLogger function in cflib

def wait_for_position_estimator(scf):
    print('Waiting for estimator to find stable position...')


    log_config = LogConfig(name='Kalman Variance', period_in_ms=500)
    log_config.add_variable('kalman.varPX', 'float')
    log_config.add_variable('kalman.varPY', 'float')
    log_config.add_variable('kalman.varPZ', 'float')

    var_y_history = [1000] * 10
    var_x_history = [1000] * 10
    var_z_history = [1000] * 10

    threshold = 0.001

    with SyncLogger(scf, log_config) as logger:
        for log_entry in logger:
            data = log_entry[1]

            var_x_history.append(data['kalman.varPX'])
            var_x_history.pop(0)
            var_y_history.append(data['kalman.varPY'])
            var_y_history.pop(0)
            var_z_history.append(data['kalman.varPZ'])
            var_z_history.pop(0)

            min_x = min(var_x_history)
            max_x = max(var_x_history)
            min_y = min(var_y_history)
            max_y = max(var_y_history)
            min_z = min(var_z_history)
            max_z = max(var_z_history)

'Waiting for estimator to find stable position... '
            '(QTM needs to be connected and providing data)'
        )

        log_config = LogConfig(name='Kalman Variance', period_in_ms=500)
        log_config.add_variable('kalman.varPX', 'float')
        log_config.add_variable('kalman.varPY', 'float')
        log_config.add_variable('kalman.varPZ', 'float')

        var_y_history = [1000] * 10
        var_x_history = [1000] * 10
        var_z_history = [1000] * 10

        threshold = 0.001

        with SyncLogger(cf, log_config) as log:
            for log_entry in log:
                data = log_entry[1]

                var_x_history.append(data['kalman.varPX'])
                var_x_history.pop(0)
                var_y_history.append(data['kalman.varPY'])
                var_y_history.pop(0)
                var_z_history.append(data['kalman.varPZ'])
                var_z_history.pop(0)

                min_x = min(var_x_history)
                max_x = max(var_x_history)
                min_y = min(var_y_history)
                max_y = max(var_y_history)
                min_z = min(var_z_history)
                max_z = max(var_z_history)