How does FunctionParameter() work

[loveinSH]

Hello, when I look into the code follows, I found that we can not find the value of Exchange-current density for stripping directly. Neither in code lithium_ion_parameters nur in code plating. I want to know where did PyBaMM give the definition and the equation of Exchange-current density for stripping or how does FunctionParameter() works.
Thank you for the reply.
def j0_stripping_dimensional(self, c_e, c_Li, T):
"""Dimensional exchange-current density for stripping [A.m-2]"""
inputs = {
"Electrolyte concentration [mol.m-3]": c_e,
"Plated lithium concentration [mol.m-3]": c_Li,
"Temperature [K]": T,
}
return pybamm.FunctionParameter(
"Exchange-current density for stripping [A.m-2]", inputs
)

[valentinsulzer]

it's in whichever parameter file is being used (e.g. if using ParameterValues("Chen2020") it's in Chen2020.py)