infer([im[arm.roi.y:arm.roi.y + arm.roi.h, arm.roi.x:arm.roi.x + arm.roi.w].resize(28,20) for arm in arms])

It is difficult to infer the exact meaning of this code snippet without additional context. However, it appears to be processing an image by cropping out regions of interest (ROIs) corresponding to the arm in the image, resizing each ROI to a fixed size (28x20), and then storing the processed ROIs in a list. The "infer" function may be used to perform additional analysis or classification on these processed ROIs.