Dear ChimeraX users, 

I'm trying to write a script that will export an attribute file in ChimeraX, (specifically the attribute sasa) I'm looking for a similar output to that of the attribute calculator function in Chimera (see image below) 

I'm currently trying to run the command below to export the attribute file:

However, when I run this script, it produces the error: "No known data format for file suffix '.defattr'" 

Any advice on how I can better go about producing this file or how I can modify my script to prevent this error would be greatly appreciated. 

Thank you for your time. 

Kind regards,

David