Animation animation in Unity is played backwards and forwards

public Animation animation;

void Start()
{
   PlayAnimBack(Animation animation);
}
/// <summary>
/// Animation reverse
/// </summary>
/// <param name="animation"></param>
public void PlayAnimBack(Animation animation)
{
    if(animation!=null)
    {
        animation[animation.clip.name].time = animation[animation.clip.name].length;
        animation[animation.clip.name].speed = -1;
        animation.Play(animation.clip.name);
    }
}
/// <summary>
///Animation reverse
/// </summary>
/// <param name="animation"></param>
public void PlayAnim(Animation animation)
{
    if(animation!=null)
    {
        animation[animation.clip.name].time = 0;
        animation[animation.clip.name].speed = 1;
        animation.Play(animation.clip.name);
    }
}