toJson method
Converts to JSON
Implementation
Map<String, dynamic> toJson() => {
'id': id,
if (filename != null) 'filename': filename,
if (extension != null) 'extension': extension,
if (size != null) 'size': size,
if (audioDuration != null) 'audio_duration': audioDuration,
if (numberOfChannels != null) 'number_of_channels': numberOfChannels,
};