code: func GetPacketNumberLength(packetNumber PacketNumber) PacketNumberLen {
  	if packetNumber < (1 << (uint8(PacketNumberLen1) * 8)) {
  		return PacketNumberLen1
  	}
  	if packetNumber < (1 << (uint8(PacketNumberLen2) * 8)) {
  		return PacketNumberLen2
  	}
  	if packetNumber < (1 << (uint8(PacketNumberLen3) * 8)) {
  		return PacketNumberLen3
  	}
  	return PacketNumberLen4
  }
docs: // GetPacketNumberLength gets the minimum length needed to fully represent the packet number