Function nesta_cone_fill 

fn nesta_cone_fill(
    chi_init: &[f64],
    cone: &[bool],
    masks: &HomogeneityMasks,
    grid: &Grid,
    params: &HeidiParams,
    progress: impl FnMut(usize, usize),
) -> Vec<f64>

NESTA with continuation: fill the dipole cone under a weighted-TV prior while holding the well-conditioned coefficients of chi_init fixed.