How to modify anchor size to detect smaller objects and use multiple anchors of different dimension

[YogeshShitole]

I have four different prior boxes (anchors) with width and length dimension a1 = (w1, l1) a2 = (w2, l2) a3 = (w3, l3) a4 = (w4, l4)

how to use these pror box anchors in place of standard anchors generated by faster_rcnn_pytorch/faster_rcnn/rpn_msr/generate_anchors.py