code: public static String asPath(File file) {
          if (file == null) {
              return null;
          }
          return asPath(file.getPath());
      }
docs: platform independent file.getPath()
  
  @param file the file to transform, or {@code null}
  @return The result of file.getPath() with all path Separators beeing a "/", or {@code null}
  Needed to transform Windows path separators into slashes.