As raised in #411, this should be fixed by something like not isinstance(cell, tuple) and not len(cell) in (3, 4) as @sphuber suggested.

cell is defined at https://spglib.readthedocs.io/en/latest/python-interface.html#crystal-structure-cell. I think cell can be given by list or something like that. How should we do? Do you have any idea @lan496, @LecrisUT?