open method
- FileMode mode = FileMode.read,
override
    Opens the file for random access operations.
Returns a Future<RandomAccessFile> that completes with the opened
random access file. RandomAccessFiles must be closed using the
RandomAccessFile.close method.
Files can be opened in three modes:
- 
FileMode.read: open the file for reading. 
- 
FileMode.write: open the file for both reading and writing and truncate the file to length zero. If the file does not exist the file is created. 
- 
FileMode.append: same as FileMode.write except that the file is not truncated. 
Throws a FileSystemException if the operation fails.
Implementation
@override
Future<RandomAccessFile> open({
  FileMode mode = FileMode.read,
}) =>
    delegate.open(mode: mode);