def METHOD_NAME(
    signature: Ed25519Signature, digest: bytes, pub_key: Ed25519PublicPoint
) -> None:
    """Verify Ed25519 signature. Raise exception if the signature is invalid.
    A CoSi combined signature is equivalent to a plain Ed25519 signature with a public
    key that is a combination of the cosigners' public keys. This function takes the
    combined public key and performs simple Ed25519 verification.
    """
    # XXX this *might* change to bool function
    _ed25519.checkvalid(signature, digest, pub_key)