Method challenges

delegatable_credentials/src/set_commitment.rs:596–615

(
        n: u32,
        commitments: &[SetCommitment<E>],
        subsets: &[BTreeSet<E::ScalarField>],
    )

    }

    fn challenges<D: Digest>(
        n: u32,
        commitments: &[SetCommitment<E>],
        subsets: &[BTreeSet<E::ScalarField>],
    ) -> Vec<E::ScalarField> {
        le_bytes_iter(n)
            .zip(commitments)
            .zip(subsets)
            .map(|((ctr_bytes, c), s)| {
                let mut bytes = vec![];
                bytes.extend_from_slice(&ctr_bytes);
                c.serialize_compressed(&mut bytes).unwrap();
                for j in s {
                    j.serialize_compressed(&mut bytes).unwrap()
                }

                field_elem_from_try_and_incr::<_, D>(&bytes)
            })
            .collect()
    }
}

// TODO: Add DisjointsetWitness