omega should be a keyword argument

[alexdenker]

Regarding: https://github.com/ucl-bug/lbs/blob/6203890e73394b981730504c788f0c6c152dc732/bno/datasets.py#L163C1-L163C71

omega should be a keyword argument, i.e., change to
sim_params = helmholtz.default_params(src, medium, omega=self.omega)