A confusion aroused by the sample 4 from official manual

[draftman9]

I am trying to study this pkg by reproducing the official manual. When I tryied the sample 4, I was confused by the function $H_t$ :

And I found it in the official website:

timeevolution.master_dynamic(tspan, rho0, f; )
f: Function f(t, rho) -> (H, J, Jdagger) or f(t, rho) -> (H, J, Jdagger, rates)

I think the $\rho$(rho) is unnecessary because I found the variable was not used in the $H_t$ function and the program ran well when I changed it into xxxx that would not be used in the $H_t$ function.

So I am really confused by the unused $\rho$(rho). Is there anything I neglected?

[ChristophHotter]

Hi @draftman9,
Yes this might be a little bit confusing, but it is simply syntax:
The third argument of master_dynamic needs to be a function which has two arguments. The first argument is the time variable and the second the (current) density matrix of the system (since the Hamiltonian, jumps or rates could depend on it). The names of theses variables do not matter.