Function batch_lif_run_varying 

pub(crate) fn batch_lif_run_varying<'py>(
    py: Python<'py>,
    leak_k: i16,
    gain_k: i16,
    currents: PyReadonlyArray1<'py, i16>,
    noises: Option<PyReadonlyArray1<'py, i16>>,
    data_width: u32,
    fraction: u32,
    v_rest: i16,
    v_reset: i16,
    v_threshold: i16,
    refractory_period: i32,
) -> PyResult<(Bound<'py, PyArray1<i32>>, Bound<'py, PyArray1<i16>>)>

Run a LIF neuron for N steps with per-step current and optional noise arrays.