Using custom data importer

Hello, I am trying to add nlu data in a json file programmatically by using a custom importer inheriting TrainingDataImporter. How should I implement the get_config_file_for_auto_config method ? This is what I have tried because it’s abstract, neither can I leave it unimplemented nor return another path because “Auto-config for multiple importers is not supported”

def get_config_file_for_auto_config(self):
        pass

Anyway I am getting this error even when I return a file path:

Traceback (most recent call last):
  File "/home/winner/NEW/Kara/venv/bin/rasa", line 8, in <module>
    sys.exit(main())
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/__main__.py", line 110, in main
    cmdline_arguments.func(cmdline_arguments)
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/cli/train.py", line 62, in <lambda>
    train_parser.set_defaults(func=lambda args: run_training(args, can_exit=True))
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/cli/train.py", line 94, in run_training
    training_result = train_all(
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/api.py", line 105, in train
    return train(
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/model_training.py", line 160, in train
    return _train_graph(
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/model_training.py", line 202, in _train_graph
    config, _missing_keys, _configured_keys = recipe.auto_configure(
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/engine/recipes/default_recipe.py", line 869, in auto_configure
    DefaultV1Recipe._dump_config(
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/engine/recipes/default_recipe.py", line 964, in _dump_config
    config_as_expected = DefaultV1Recipe._is_config_file_as_expected(
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/engine/recipes/default_recipe.py", line 1009, in _is_config_file_as_expected
    content = rasa.shared.utils.io.read_config_file(config_file_path)
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/shared/utils/io.py", line 589, in read_config_file
    return read_validated_yaml(filename, CONFIG_SCHEMA_FILE)
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/shared/utils/io.py", line 570, in read_validated_yaml
    content = read_file(filename)
  File "/home/winner/NEW/Kara/venv/lib/python3.8/site-packages/rasa/shared/utils/io.py", line 126, in read_file
    with open(filename, encoding=encoding) as f:
TypeError: expected str, bytes or os.PathLike object, not NoneType

Please somebody help