def METHOD_NAME(self):
    param = pybamm.LithiumIonParameters()
    model_n = pybamm.interface.BaseInterface(
        param, "negative", "lithium-ion main", {}
    )
    model_n.options = self.options
    j0_n = model_n._get_exchange_current_density(self.variables)
    model_p = pybamm.interface.BaseInterface(
        param, "positive", "lithium-ion main", {}
    )
    model_p.options = self.options
    j0_p = model_p._get_exchange_current_density(self.variables)
    # Process parameters
    parameter_values = pybamm.lithium_ion.BaseModel().default_parameter_values
    j0_n = parameter_values.process_symbol(j0_n)
    j0_p = parameter_values.process_symbol(j0_p)
    # Test
    for x in j0_n.pre_order():
        self.assertNotIsInstance(x, pybamm.Parameter)
    for x in j0_p.pre_order():
        self.assertNotIsInstance(x, pybamm.Parameter)