An issue in `data_gen/src/data_io.py` for `isinstance(field, CenteredGrid) `

When I ran the command `python gen_ns_incomp.py`, I encountered the below error:

 File "/home/liyezhang/hzh/PDEBench/pdebench/data_gen/src/data_io.py", line 68, in to_centre_grid
    if isinstance(field, CenteredGrid):
TypeError: isinstance() arg 2 must be a type or tuple of types

How I can solve this problem?