Function decompose 

pub fn decompose(
    signal: &[f64],
    family: WaveletFamily,
    mode: BoundaryMode,
    level: Option<usize>,
) -> Result<WaveletCoeffs, FdarError>

Multi-level orthogonal DWT: decompose a signal into a Mallat coefficient pyramid.

Applies [single_level_analysis] repeatedly to the running approximation band, collecting one detail band per level (finest-first). When level is None the depth defaults to max_level; an explicit level is validated to lie in 1..=max_level.

Errors

• FdarError::InvalidParameter if signal is empty, the family is unsupported, or an explicit level is 0 or exceeds max_level.