code: def df_ambig(df):
      """DataFrame with levels 'L1' and 'L2' and labels 'L1' and 'L3'"""
      df = df.set_index(["L1", "L2"])
  
      df["L1"] = df["L3"]
  
      return df
  
imports: import pytest
  from pandas.core.dtypes.missing import array_equivalent
  import pandas
label_desc: Use image node_id 3 for calling a global function with example usage: df_ambig(df) and returns: df