FileSystemSink constructor
Creates a new FileSystemSink writing to path on fs.
Implementation
FileSystemSink(this.fs, this.path, this.baseEpochUs) {
_file = fs.file(path);
if (!_file.parent.existsSync()) {
_file.parent.createSync(recursive: true);
}
_ios = _file.openWrite(mode: FileMode.write);
_ios.write('[\n');
}