code: def test_strings(self):
      df = pd.DataFrame({"a": ["string", "string2", "string3"]})
      ds = ray.data.from_pandas(df)
      prep = Concatenator(output_column_name="huh")
      new_ds = prep.transform(ds)
      assert "huh" in set(new_ds.schema().names)
  
file_path: ray/python/ray/data/tests/preprocessors/test_concatenator.py
imports: import numpy
  import pandas
  import pytest
  import ray
  from ray.data.preprocessors import Concatenator
label_desc: Use image node_id 6 for calling the TestConcatenator obj's underlying member method code with example usage: obj.test_strings() without return types