Error in custom defined funtion

[SP171995]

python version 3.8.3
pybamm version 23.2

I have defined a new function for electrode diffusivity as function of c_s_surf and using lookup table for concentration and diffusion coefficients :

def solid_state_diff_graphite (c_s_surf) :
print(c_s_surf)
x = np.array([0,...,1])
y = np.array([])
D_s_graphite = pybamm.Interpolant(x, y, c_s_surf, interpolator='linear')
return D_s_graphite

def solid_state_diff_nmc (c_s_surf) :
x = np.array([0,...,1])
y = np.array([.....])
D_s_nmc = pybamm.Interpolant(x, y, c_s_surf, interpolator='linear')
return D_s_nmc

but I am getting an error as follows
TypeError: solid_state_diff_graphite() takes 1 positional argument but 2 were given

i also tried using self
def solid_state_diff_nmc (self,c_s_surf) :

but this is not calling c_s_surf insted it is taking it as Reference Temperature and interpolation is failing

[valentinsulzer]

Look at existing parameter sets to see which inputs are required

[SP171995]

so existing parameter set just has one value of diffusion coefficient but I have defined it now as
"Negative electrode diffusivity [m2.s-1]": solid_state_diff_graphite,
"Positive electrode diffusivity [m2.s-1]": solid_state_diff_nmc,

if I define the function as "def solid_state_diff_graphite (self,c_s_surf) : "
then code is taking c_s_surf as scalar value 298.15

[valentinsulzer]

https://github.com/pybamm-team/PyBaMM/blob/develop/pybamm/input/parameters/lithium_ion/OKane2022.py look at how it's defined here