code: def split_train_test(df):
      train_df = df.sample(frac=0.8, random_state=0)
      test_df = df.drop(train_df.index)
      return train_df, test_df
  
file_path: BigDL/python/orca/tutorial/xshards/auto_mpg.py
imports: import math
  import bigdl.orca.data.pandas
  from bigdl.orca import init_orca_context, stop_orca_context
  from bigdl.orca.data.transformer import *
  from bigdl.orca.learn.tf2.estimator import Estimator
  import tensorflow.compat.v1
  from tensorflow.keras.models import Sequential
  from tensorflow.keras.layers import Dense
label_desc: Use image node_id 3 for calling a global function with example usage: split_train_test(df) and returns: train_df,  test_df