generalized forcing function?

HI,
I am trying to generate a dataset for forcing function f = sin(4y)ˆ x−0.1u, (as is used in [1]).

How can I perform that with this code? From what I understand, only sinusoidal forcing functions are allowed yet.
would you please help me know how to implement this forcing function as well?

TIA.
[1]: https://arxiv.org/abs/2308.05732