Function min_budget_for_credulous 

pub fn min_budget_for_credulous<A>(
    framework: &WeightedFramework<A>,
    target: &A,
) -> Result<Option<f64>, Error>
where
    A: Clone + Eq + Hash + Debug + Ord,

Return the smallest budget at which target is credulously accepted, or None if it is never accepted across the framework’s full budget range.

Under Dunne 2011 semantics, credulous acceptance is monotone in β, so the returned value is a stable threshold: once the target is accepted, it remains accepted for all larger budgets.