code: def test_datasets_empty_metadata(self):
      record = TextClassificationRecord(text="mock")
      dataset = DatasetForTextClassification([record])
      assert dataset.to_datasets()["metadata"] == [None]
  
imports: import copy
  import os
  import sys
  from time import sleep
  import datasets
  import pandas
  import pytest
  import spacy
  from argilla.client.datasets import DatasetBase, DatasetForText2Text, DatasetForTextClassification, DatasetForTokenClassification, WrongRecordTypeError, read_datasets, read_pandas
  from argilla.client.models import Text2TextRecord, TextClassificationRecord, TokenClassificationRecord
  from argilla.datasets import TextClassificationSettings
label_desc: Use image node_id 4 for calling the TestDatasetForTextClassification obj's underlying member method code with example usage: obj.test_datasets_empty_metadata() without return types