Function suggest 

pub fn suggest(
    sampler: &dyn Sampler,
    view: &StudyView,
    seed: u64,
    number: u64,
) -> Result<Assignment>

Asks sampler for the next point, given the history in view.

Derives the trial’s seed from (seed, number), infers the relative space (for a declared-space view that is the schema verbatim) and samples it jointly — the same three steps the real study loop performs at ask time.

Errors

Whatever the sampler reports: an inference failure or a malformed distribution (Error::Sampler / Error::InvalidSpace).