code: function restoreFile($path, $rev)
      {
          Path::checkArgNonRoot("path", $path);
          Checker::argStringNonEmpty("rev", $rev);
  
          $response = $this->doPost(
              $this->apiHost,
              $this->appendFilePath("1/restore", $path),
              array("rev" => $rev));
  
          if ($response->statusCode === 404) return null;
          if ($response->statusCode !== 200) throw RequestUtil::unexpectedStatus($response);
  
          return RequestUtil::parseResponseJson($response->body);
      }
docs: Takes a copy of the file at the given revision and saves it over the current copy.  This
  will create a new revision, but the file contents will match the revision you specified.
  
  See <a href="https://www.dropbox.com/developers/core/docs#restore">/restore</a>.
  
  @param string $path
  The Dropbox path of the file to restore (UTF-8).
  
  @param string $rev
  The revision to restore the contents to.
  
  @return mixed
  The <a href="https://www.dropbox.com/developers/core/docs#metadata-details">metadata
  object</a>
  
  @throws Exception