How to use custom PPS with DefaultRenderPipeline?

Hi everybody~
I have created a screen space postprocess, I think it should be renderred before DefaultRenderPipeline. I find this doc:

I am not really sure how the PostProcessRenderPipelineManager work.
If I create 3 pipeline a,b,c, and then
scene.postProcessRenderPipelineManager.addPipeline(a); scene.postProcessRenderPipelineManager.addPipeline(b);
Does it render from scene→a→b→c? or it has other api to decide the render order of those 3 pipeline?

They should be rendered in order they have been added into the manager.

Thank you for your help!