How to access a Resnet layer output when using an FPN backbone?

[anujstam]

Hello!
I want to use an FPN backbone, but I also require the outputs of the Res4 and Res5 layers of the resnet in my model. When using the FPN, I am unable to access the res4 and res5 features, and can only access p2 to p6.

Is there an easy way to do this or do I need to write my own backbone?