Function synthseg 

pub fn synthseg(
    magnitude: &[f64],
    grid: &Grid,
    affine: &[f64; 16],
    model_onnx: &[u8],
    params: &SynthSegParams,
    progress: impl FnMut(usize, usize),
) -> Result<SynthSegResult, OnnxError>

Whole-brain segmentation via SynthSeg.

• magnitude — magnitude image, column-major (nx, ny, nz). Not a susceptibility map; see the module docs.
• affine — the image’s NIfTI affine (row-major 4×4), used to find the RAS orientation.
• model_onnx — bytes of the exported synthseg.onnx (see crate::models).
• progress(done, total) — called after each network evaluation.