code: def test_get_tfds_id_prefixes_single_directory(self):
      file_instructions = [
          shard_utils.FileInstruction("/a/b/f1", 0, -1, 1),
          shard_utils.FileInstruction("/a/b/f2", 0, -1, 1),
      ]
      actual = reader_lib._get_tfds_id_prefixes(file_instructions)
      self.assertEqual(actual, {"/a/b/f1": "f1", "/a/b/f2": "f2"})
  
imports: import functools
  import itertools
  import os
  from unittest import mock
  import tensorflow
  import tensorflow_datasets
  from tensorflow_datasets import testing
  from tensorflow_datasets.core import example_parser
  from tensorflow_datasets.core import naming
  from tensorflow_datasets.core import reader
  from tensorflow_datasets.core import splits
  from tensorflow_datasets.core import writer
  from tensorflow_datasets.core.utils import read_config
  from tensorflow_datasets.core.utils import shard_utils
label_desc: Use image node_id 1 for calling the AddTfdsIdTest obj's underlying member method code with example usage: obj.test_get_tfds_id_prefixes_single_directory() without return types