I am trying to create python bindings to a vala library using pygi with gobject introspection. However, I am having trouble generating the GIR files (that I am planning to compile to typelib files subsequently). According to the documentation valac should support generating GIR files.

Compiling the following

helloworld.vala

public struct Point {
    public double x;
    public double y;
}

public class Person {

    public int age = 32;

    public Person(int age) {
        this.age = age;
    }

}

public int main() {

    var p = Point() { x=0.0, y=0.1 }; 
    stdout.printf("%f %f\n", p.x, p.y);

    var per = new Person(22);
    stdout.printf("%d\n", per.age);

    return 0;

}

with the command

valac helloworld.vala --gir=Hello-1.0.gir

doesn't create the Hello-1.0.gir file as one would expect. How can I generate the gir file?