Function py_gpfa 

pub(crate) fn py_gpfa<'py>(
    py: Python<'py>,
    trains: Vec<PyReadonlyArray1<'py, i32>>,
    n_latents: usize,
    bin_ms: f64,
    dt: f64,
    max_iter: usize,
    tol: f64,
    seed: u64,
) -> PyResult<Bound<'py, PyDict>>