Persist role model

def save(self, role, commit=True):
        """ Persist role model """
        self.is_instance(role)

        schema = RoleSchema()
        valid = schema.process(role)
        if not valid:
            return valid

        db.session.add(role)
        if commit:
            db.session.commit()

        events.role_saved_event.send(role)
        return role