serialize method
Implementation
@override
ByteData serialize() {
var data_ = ByteData(mavlinkEncodedLength);
data_.setUint8(0, targetSystem);
data_.setUint8(1, targetComponent);
data_.setUint8(2, directoryType);
data_.setUint8(3, startIndex);
data_.setUint8(4, count);
MavlinkMessage.setInt8List(data_, 5, directoryData);
return data_;
}