Function recon_phase 

fn recon_phase(
    te: &[f64],
    _b0: f64,
    den: f64,
    model: impl Fn(f64) -> (f64, f64),
) -> f64

Reconstruct a source value: −Σ angle(model(TE)) / den, with the phase unwrapped along the echo axis so a strong source is not folded back to zero (see unwrap_near).