How to Redefine Core Parameter Functions (e.g., Exchange Current Density) with Custom Functional Forms?

[vipulramk]

I'm working with PyBaMM and need to modify the functional form of certain parameters that are already defined in the core library. Specifically, I want to change how exchange current density is calculated.

Current situation:
The exchange current density is currently defined as a function of cs (surface concentration), cs_max, ce (electrolyte concentration), and T (temperature).

What I want to do:
I'd like to redefine it as a function of stoichiometry and temperature instead, using a different mathematical relationship.

What's the proper way to override or redefine the core functional definition of these parameters in PyBaMM?
Any guidance on the recommended approach would be appreciated.

[rtimms]

In general, you cannot do this without editing the model code. In your case, you can just do something like

def exchange_current_density(c_e, c_s_surf, c_s_max, T):
    sto = c_s_surf / c_s_max
    return # function of (sto, T) here...