func IsFrameRetransmittable(f wire.Frame) bool {
	switch f.(type) {
	case *wire.AckFrame:
		return false
	default:
		return true
	}
}
IsFrameRetransmittable returns true if the frame should be retransmitted.
package ackhandler
import "github.com/lucas-clemente/quic-go/internal/wire"
func stripNonRetransmittableFrames(fs []wire.Frame) []wire.Frame {
	res := make([]wire.Frame, 0, len(fs))
	for _, f := range fs {
		if IsFrameRetransmittable(f) {
			res = append(res, f)
		}
	}
	return res
}