How to overrite the code to collect action datas from others robot？

[tjh-flash]

Hey，I have got a problem when i try to overwrite the code of lerobot to collect action datas from my own robot. Here‘s the detail. My robot is a single six joint robot arm, so i make a new RobotConfig, which only contains the info of the camera. And then I overwrite the fuction 'teleop_step' in file manipulator.py. I also set a default value of the robot pos to test at first. When i start to record, the datad of observation and action are fine, but when it comes to call the function 'save_eposide', error comes up, which i show below. I reall want to know what else should i suppose to do to make it work, thanks.

[tjh-flash]

Here is the error info.