Function bbs_proof_verify 

pub fn bbs_proof_verify(
    public_key: &[u8],
    proof: &[u8],
    disclosed_messages: &[(usize, Vec<u8>)],
    header: Option<&[u8]>,
    nonce: Option<&[u8]>,
) -> Result<bool, BbsError>

Verify a BBS+ zero-knowledge proof.