get_primitive() fails with pymatgen ≥ 2022

pymatgen ≥ 2022 only accepts keyword arguments:

    structure.to(filename=path, fmt="cif")   # OK
    structure.to("cif", path)                # raises ValueError

One-line fix in `MOF_descriptors.py`:

-    sprim.to("cif", write_path)
+    sprim.to(filename=write_path, fmt="cif")

Hope this tiny bug can be fixed soon. Thanks!