Function verify 

pub fn verify<Msg, HashToField, Point, Scalar>(
    generator: &Point,
    message: &Msg,
    public_key: &Point,
    _: &Signature<Point, Scalar>,
    hash_to_field: HashToField,
) -> bool
where
    Msg: ?Sized,
    HashToField: FnOnce(&Point, &Point, &Msg) -> Scalar,
    Point: CofactorGroup + Group<Scalar = Scalar>,
    Scalar: PrimeField,

Verify a signature.

The group arithmetic uses generator to produce public keys.