code: def test_concatenate_columns(dataframe):
      """Basic test for concatenate_columns."""
      df = dataframe.concatenate_columns(
          column_names=["a", "decorated-elephant"],
          sep="-",
          new_column_name="index",
      )
      assert "index" in df.columns
  
imports: import pytest
  from janitor.errors import JanitorError
label_desc: Use image node_id 1 for calling a global function with example usage: test_concatenate_columns(dataframe) without return types