def METHOD_NAME(self):
    def external_circuit_function(variables):
        I = variables["Current [A]"]
        V = variables["Voltage [V]"]
        return V + I - pybamm.FunctionParameter("Function", {"Time [s]": pybamm.t})
    options = {"operating mode": external_circuit_function}
    model = pybamm.lithium_ion.MPM(options)
    model.check_well_posedness()