Code bug

[kjz1997]

Hello professor, while reading the code in the era.py file, I noticed that there seems to be some issue with line 112. The code means to read the potential height, but when I tested using the era5 data in the test file, I found that grb [0] read the specific humidity, and the index of the potential height index is 2, not 0. I am not sure if my understanding is correct. Looking forward to your reply。