code: def main(unused_argv):
      if FLAGS.dataframes == "spark":
          compute_on_spark_dataframes()
      else:
          raise ValueError(
              f"{FLAGS.dataframes} dataframes are not supported."
          )
      return 0
  
file_path: pipelinedp/examples/restaurant_visits/run_on_dataframes.py
imports: from absl import app
  from absl import flags
  import os
  import shutil
  import pandas
  from pyspark.sql import SparkSession
  import pyspark
  import apache_beam
  from apache_beam.runners.portability import fn_api_runner
  from apache_beam.dataframe.io import read_csv
  import pipeline_dp
  from pipeline_dp import dataframes
  from typing import Union
label_desc: Use image node_id 5 for calling a global function with example usage: main(unused_argv) and returns: int