code: @Implementation(minSdk = KITKAT)
    protected boolean sendVendorSpecificResultCode(
        BluetoothDevice device, String command, String arg) {
      if (command == null) {
        throw new IllegalArgumentException("Command cannot be null");
      }
      return allowsSendVendorSpecificResultCode && connectedDevices.contains(device);
    }
docs: Overrides behavior of {@link sendVendorSpecificResultCode}.
  
  @return 'true' only if the given device has been previously added by a call to {@link
  ShadowBluetoothHeadset#addConnectedDevice} and {@link
  ShadowBluetoothHeadset#setAllowsSendVendorSpecificResultCode} has not been called with
  'false' argument.
  @throws IllegalArgumentException if 'command' argument is null, per Android API