code: public static void deleteContentsRecursive(@Nonnull File file) throws IOException {
          deleteContentsRecursive(fileToPath(file), PathRemover.PathChecker.ALLOW_ALL);
      }
docs: Deletes the contents of the given directory (but not the directory itself)
  recursively.
  It does not take no for an answer - if necessary, it will have multiple
  attempts at deleting things.
  
  @throws IOException
  if the operation fails.