code: func (h *receivedPacketHistory) DeleteBelow(p protocol.PacketNumber) {
  	if p <= h.lowestInReceivedPacketNumbers {
  		return
  	}
  	h.lowestInReceivedPacketNumbers = p
  
  	nextEl := h.ranges.Front()
  	for el := h.ranges.Front(); nextEl != nil; el = nextEl {
  		nextEl = el.Next()
  
  		if p > el.Value.Start && p <= el.Value.End {
  			el.Value.Start = p
  		} else if el.Value.End < p { // delete a whole range
  			h.ranges.Remove(el)
  		} else { // no ranges affected. Nothing to do
  			return
  		}
  	}
  }
docs: // DeleteBelow deletes all entries below (but not including) p