Function lbv 

pub fn lbv(
    field: &[f64],
    mask: &[u8],
    nx: usize,
    ny: usize,
    nz: usize,
    vsx: f64,
    vsy: f64,
    vsz: f64,
    tol: f64,
    max_iter: usize,
) -> (Vec<f64>, Vec<u8>)

Returns

Tuple of (local_field, eroded_mask)