Function process_segment 

pub fn process_segment(
    segment: &[f64],
    sample_rate: f64,
    nfft: usize,
    nlap: usize,
    response: &Response,
    psd_periods: &[f64],
    bin_left: &[f64],
    bin_right: &[f64],
) -> Result<Vec<Option<f64>>>

Process one PPSD segment, replicating ObsPy’s PPSD.__process exactly.

Performs the full pipeline:

1. Welch PSD — mlab.psd with cosine taper and linear detrend
2. Reorder — skip DC bin, reverse to period order
3. Response removal — divide by |H(f)|² and multiply by ω² (velocity→acceleration)
4. dB conversion — 10 × log₁₀(PSD)
5. Period bin averaging — octave-spaced bins

Takes stationxml_rs::Response directly — no intermediate types needed.

Arguments

• segment — Time-domain samples for one PPSD segment.
• sample_rate — Sampling rate in Hz.
• nfft — FFT length for Welch’s method.
• nlap — Overlap samples for Welch’s method.
• response — Instrument response from stationxml_rs::Channel.
• psd_periods — Period values (seconds) from the Welch FFT.
• bin_left — Left edges of period bins (seconds).
• bin_right — Right edges of period bins (seconds).

Returns

Vector of Option<f64> — dB values per period bin. None for empty bins.

Errors

Returns PpsdError if response evaluation fails (see eval_response).