def METHOD_NAME(side):
    # returns the flux at a separator/electrode interface
    # assuming v_box = 0 for now
    return (
        pybamm.boundary_value(
            -(1 - param.t_plus(c_e, T)) / (tor * param.D_e(c_e, T) * param.F),
            side,
        )
        * i_boundary_cc
    )