method promises.FileHandle.sync
Usage in Deno
```typescript import { type promises } from "node:node__fs.d.ts"; ```
FileHandle.sync(): Promise<void>
Request that all data for the open file descriptor is flushed to the storage
device. The specific implementation is operating system and device specific.
Refer to the POSIX [`fsync(2)`](http://man7.org/linux/man-pages/man2/fsync.2.html) documentation for more detail.
Promise<void>
Fulfills with `undefined` upon success.