I'm trying to create a fmu of a custom class. My code is structured like this:

from pythonfmu.fmi2slave import Fmi2Slave, Fmi2Causality, Fmi2Variability, Real try: import MyModel as mymodel from sympy import symbols, exp except ImportError: symbols, exp, mymodel = None, None, None class MyFmu(Fmi2Slave): def __init__(self, **kwargs): super().__init__(**kwargs) self.input_var = 0. self.output_var = 0. self.model = mymodel.ModelClass(...) self.register_variable(Real('input_var', causality=Fmi2Causality.input)) self.register_variable(Real('output_var', causality=Fmi2Causality.output)) def do_step(self, current_time, step_size) -> bool: self.output_var = self.model.step(...) return True 

I followed the sympyslave.py structure to declare the imports, even if I don't plan to use sympy.

My problem is related to the import of MyModel.py script, which is a custom script that I would like to wrap with fmu.

I'm trying to export the fmu with this command pythonfmu build -f MyFmu.py MyModel.py because I'm considering MyModel.py as a project file, but it's not working since I'm getting the error AttributeError: 'NoneType' object has no attribute 'Model'.

Am I missing something or is it just unfeasible to import a custom class in this way?
Thanks in advance for the help.