code: def drop_na(df):
      df = df.dropna()
      return 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 1 for calling a global function with example usage: drop_na(df) and returns: df