How to use the ihatemoney.models.db.session.add function in ihatemoney

form = ProjectForm()
    if request.method == "GET" and "project_id" in request.values:
        form.name.data = request.values["project_id"]

    if request.method == "POST":
        # At first, we don't want the user to bother with the identifier
        # so it will automatically be missing because not displayed into
        # the form
        # Thus we fill it with the same value as the filled name,
        # the validation will take care of the slug
        if not form.id.data:
            form.id.data = form.name.data
        if form.validate():
            # save the object in the db
            project = form.save()
            db.session.add(project)
            db.session.commit()

            # create the session object (authenticate)
            session[project.id] = True
            session.update()

            # send reminder email
            g.project = project

            message_title = _(
                "You have just created '%(project)s' " "to share your expenses",
                project=g.project.name,
            )

            message_body = render_template(
                "reminder_mail.%s.j2" % get_locale().language

"reset_password.html", form=form, error=_("No token provided")
        )
    project_id = Project.verify_token(token)
    if not project_id:
        return render_template(
            "reset_password.html", form=form, error=_("Invalid token")
        )
    project = Project.query.get(project_id)
    if not project:
        return render_template(
            "reset_password.html", form=form, error=_("Unknown project")
        )

    if request.method == "POST" and form.validate():
        project.password = generate_password_hash(form.password.data)
        db.session.add(project)
        db.session.commit()
        flash(_("Password successfully reset."))
        return redirect(url_for(".home"))
    return render_template("reset_password.html", form=form)

def post(self):
        form = ProjectForm(meta={"csrf": False})
        if form.validate() and current_app.config.get("ALLOW_PUBLIC_PROJECT_CREATION"):
            project = form.save()
            db.session.add(project)
            db.session.commit()
            return project.id, 201
        return form.errors, 400

def post(self, project):
        form = get_billform_for(project, True, meta={"csrf": False})
        if form.validate():
            bill = Bill()
            form.save(bill, project)
            db.session.add(bill)
            db.session.commit()
            return bill.id, 201
        return form.errors, 400

Create a demo project if it doesn't exists yet (or has been deleted)
    If the demo project is deactivated, one is redirected to the create project form
    """
    is_demo_project_activated = current_app.config["ACTIVATE_DEMO_PROJECT"]
    project = Project.query.get("demo")

    if not project and not is_demo_project_activated:
        raise Redirect303(url_for(".create_project", project_id="demo"))
    if not project and is_demo_project_activated:
        project = Project(
            id="demo",
            name="demonstration",
            password=generate_password_hash("demo"),
            contact_email="demo@notmyidea.org",
        )
        db.session.add(project)
        db.session.commit()
    session[project.id] = True
    return redirect(url_for(".list_bills", project_id=project.id))

def add_bill():
    form = get_billform_for(g.project)
    if request.method == "POST":
        if form.validate():
            # save last selected payer in session
            session["last_selected_payer"] = form.payer.data
            session.update()

            bill = Bill()
            db.session.add(form.save(bill, g.project))
            db.session.commit()

            flash(_("The bill has been added"))

            args = {}
            if form.submit2.data:
                args["add_bill"] = True

            return redirect(url_for(".list_bills", **args))

    return render_template("add_bill.html", form=form)

def edit_project():
    edit_form = EditProjectForm()
    if request.method == "POST":
        if edit_form.validate():
            project = edit_form.update(g.project)
            db.session.add(project)
            db.session.commit()

            return redirect(url_for(".list_bills"))
    else:
        edit_form.name.data = g.project.name
        edit_form.contact_email.data = g.project.contact_email

    return render_template(
        "edit_project.html", edit_form=edit_form, current_view="edit_project"
    )