code: def test_clean_names_camelcase_to_snake(spark_df):
      """Tests case_type parameter 'snake' takes effect."""
      spark_df = spark_df.selectExpr("a AS AColumnName").clean_names(
          case_type="snake"
      )
      assert list(spark_df.columns) == ["a_column_name"]
  
file_path: pyjanitor/tests/spark/functions/test_clean_names_spark.py
imports: import pytest
  from helpers import running_on_ci
  from janitor.errors import JanitorError
  import janitor.spark
label_desc: Use image node_id 6 for calling a global function with example usage: test_clean_names_camelcase_to_snake(spark_df) without return types