removeBehaviour(behaviour) {
    let index = this.behaviours.indexOf(behaviour);
    this.behaviours.splice(index, 1);

    if (behaviour.parents) {
      index = behaviour.parents.indexOf(behaviour);
      behaviour.parents.splice(index, 1);
    }

    return index;
  }
remove the Behaviour
@method removeBehaviour
@param {Behaviour} behaviour a behaviour