I can't save a model as a sbml file

[gcxxx]

Hi,
I create my own model 'on the fly' using cobrapy package. Now I want to save it as a sbml file, but an error occured, how to solve this problem? (By the way, I can save this model as json file, no error occured.)
I upload my model in json file.

133reactions.zip

[Midnighter]

SBML has more consistency checks than JSON. My guess is that some metabolite's compartment is set to None where SBML expects a compartment identifier. That's an issue with our SBML writer. Until it's fixed, maybe you can set it to an empty string or better yet, add a compartment to your model.