[lava-users] How to add custom data in the metadata field of notify callback json?

I want to add some key:value pair in metadata of json that POST by notification of job, but I can not figure it out. I had tried add metadata in job defination and test defination, but the back json did not have my data in metadata field, it was just a []. Then I read the lava source code, I find the metadata data are produced by method `get_metadata_dict()` in class `TestJob`. This method is called at method `create_job_data` in class `TestJob`, it creates the json data which will post to callback url. `get_metadata_dict()` check whether there is an attribute `testdata`, but I can not find the place where this attribute‘s assignment. Could someone give me a way to do this? Thanks you very much! 🙏