docs: public void setReceiverId(byte[] receiverId) {
      if (receiverId == null) {
        throw new RuntimeException("Receiver ID cannot be null.");
      }
      if (receiverId.length != DEVICE_ID_SIZE) {
        throw new RuntimeException(
            String.format("Receiver ID must be %d bytes long.",
                Integer.valueOf(DEVICE_ID_SIZE)));
      }
      this.receiverId = receiverId;
    }