Function unwrap_single 

fn unwrap_single(
    phase: &[f64],
    mag: &[f64],
    mask: &[u8],
    config: &FieldMappingConfig,
    nx: usize,
    ny: usize,
    nz: usize,
    vsx: f64,
    vsy: f64,
    vsz: f64,
    phase2: Option<&[f64]>,
    te1: f64,
    te2: f64,
) -> Vec<f64>

Unwrap a single echo using the configured algorithm.