Get the rendex index from a scene index

Hi,
I just wanted to check that I was not missing something in the hydra API on how to get the render index from an existing scene index.
My use case is the following :
I have a HdSceneIndexPlugin which is called in its _AppendSceneIndex calback to add some filtering scene index. So far so good, it works fine.
But I’d also like to insert a new scene index (injecting some new prims in the rendering) in the same render index as the scene index I am receiving in _AppendSceneIndex.
Is that possible ?
Thank you.
Regards,
David

Hi,
Answering my own question, we can use a merging scene index inside the scene index plugin callback _ApprendSceneIndex to inject som new prims in the rendering.
Regards,
David