code: def object_df(rng, long_df):
      df = long_df.copy()
      # objectify numeric columns
      for col in ["c", "s", "f"]:
          df[col] = df[col].astype(object)
      return df
  
imports: import numpy
  import pandas
  import pytest
label_desc: Use image node_id 20 for calling a global function with example usage: object_df(rng, long_df) and returns: df