Is Von Neumann stability analysis for homogenous PDE different from inhomogenous one?

Question

I'm working on nonhomogenous heat equation and the stability using Von Neumann for the implicit Euler method on $u_{t}-cu_{xx}=f(t,x)$, from the title is there any difference between the homogenous and nonhomogenous case? when applying $u_{i}^{n}=\lambda e^{ikhi}$ to the numerical method I got a term with $f$ and I don't know how can I deal with this term.. I appreciate any help:)