'Checks if a user has a particular Role at an Event.'

def _is_role(self, role_name, event_id):

    role = Role.query.filter_by(name=role_name).first()
    uer = UER.query.filter_by(user=self, event_id=event_id, role=role).first()
    if (not uer):
        return False
    else:
        return True
