code: def test__get_existing_dataset_packages(self):
      ds_packages = registered._get_existing_dataset_packages(
          "testing/dummy_config_based_datasets"
      )
      self.assertEqual(
          set(ds_packages.keys()), {"dummy_ds_1", "dummy_ds_2"}
      )
      pkg_path, builder_module = ds_packages["dummy_ds_1"]
      self.assertEndsWith(
          str(pkg_path),
          "tensorflow_datasets/testing/dummy_config_based_datasets/dummy_ds_1",
      )
      self.assertEqual(
          builder_module,
          "tensorflow_datasets.testing.dummy_config_based_datasets.dummy_ds_1.dummy_ds_1_dataset_builder",
      )
  
imports: import abc
  import re
  from unittest import mock
  import pytest
  from tensorflow_datasets import testing
  from tensorflow_datasets.core import constants
  from tensorflow_datasets.core import load
  from tensorflow_datasets.core import registered
  from tensorflow_datasets.core import splits
  from tensorflow_datasets.core import utils
  from tensorflow_datasets.core.utils import py_utils
  import tensorflow_datasets.public_api
  from tensorflow_datasets.testing.dummy_config_based_datasets.dummy_ds_1 import dummy_ds_1_dataset_builder
label_desc: Use image node_id 1 for calling the ConfigBasedBuildersTest obj's underlying member method code with example usage: obj.test__get_existing_dataset_packages() without return types