code: private ImmutableSet<File> findThriftFilesInDirectory(File directory) throws IOException {
      checkNotNull(directory);
      checkArgument(directory.isDirectory(), "%s is not a directory", directory);
      List<File> thriftFilesInDirectory = getFiles(directory, Joiner.on(",").join(includes), Joiner.on(",").join(excludes));
      return ImmutableSet.copyOf(thriftFilesInDirectory);
    }
docs: Find all {@code .thrift} files in the given directory.