# How to resolve the cif2cell TypeError?

I have encountered an error using cif2cell while covering a CIF file from COD to quantum ESPRESSO format. The error is as follows.

command typed: \$cif2cell crystal.cif -p quantum-espresso -o crystal.in

***Warning: Space group operation check failed for Hall symbol -P 1 (H-M symbol P-1). ***Warning: Site occupancies not found, assuming all occupancies = 1. Traceback (most recent call last): File “/usr/local/bin/cif2cell”, line 1574, in docstring = StandardDocstring() File “/usr/local/bin/cif2cell”, line 1021, in StandardDocstring tmpstring2 += “. Reference number : “+ref.databasecode TypeError: must be str, not NoneType

This seems to be a bug in the Quantum Mobile platform too.

• If that program (cif2cell) is still maintained, it's best to report such problems to the developers. – marcin Oct 11 '20 at 20:39

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