Function lsqr_qsm_core 

fn lsqr_qsm_core(
    local_field: &[f64],
    mask: &[u8],
    magnitude: Option<&[f64]>,
    grid: &Grid,
    bdir: (f64, f64, f64),
    params: &LsqrQsmParams,
    progress: impl FnMut(usize, usize),
) -> Vec<f64>