Get nested summaries_log_dir based on decode_hp.

def get_summaries_log_dir(decode_hp, output_dir, dataset_split):
  """Get nested summaries_log_dir based on decode_hp."""
  child_dir = decode_hp.summaries_log_dir
  level_dir = "".join([str(level) for level in decode_hp.level_interp])
  if decode_hp.channel_interp == "all":
    rank_dir = "all"
  else:
    rank_dir = "rank_%d" % decode_hp.rank_interp
  child_dir = "%s/%s_%s" % (child_dir, level_dir, rank_dir)
  if dataset_split is not None:
    child_dir += "_{}".format(dataset_split)
  return os.path.join(output_dir, child_dir)