class MyClass
{}

class MyResetableClass : IPoolable
{
  public void ResetState(){ // reset the state of this object }
}

void Demo()
{
    var o = PoolManager.Instance.GetObject<MyClass>();
    Assert.IsTrue(o != null && o.GetType() == typeof(MyClass));

    var origin = o;

    PoolManager.Instance.ReturnObject(o);
    var another = PoolManager.Instance.GetObject<MyClass>();

    Assert.IsTrue(another == origin);
}