code: public Path startLocalOutput(Path fsOutputFile, Path tmpLocalFile)
      throws IOException {
      return fs.startLocalOutput(fsOutputFile, tmpLocalFile);
    }
docs: Returns a local File that the user can write output to.  The caller
  provides both the eventual FS target name and the local working
  file.  If the FS is local, we write directly into the target.  If
  the FS is remote, we write into the tmp local area.